Javascript text functions. Description of string variables. String variable syntax

From the author: Greetings, friends. In several previous articles we got acquainted with numeric type data in JavaScript and worked with numbers. Now it's time to work with strings in JavaScript. Let's take a closer look at string type data in JavaScript.

We have already briefly become acquainted with the string type and, in fact, we only learned what a string is and how it is written. Let's now take a closer look at strings and methods for working with them.

As you remember, any text in JavaScript is a string. The string must be enclosed in quotes, single or double, it makes no difference:

var hi = "hello", name = "John";

var hi = "hello" ,

name = "John" ;

Now we have written only one word into the variables. But what if we want to record a large amount of text? Yes, no problem, let's write some fish text into a variable and output it to the console:

var text = "Lorem ipsum dolor sit amet, consectetur adipisicing elit. Nobis dignissimos maxime et tempore omnis, ab fugit. Quos nisi, culpa exercitationem!"; console.log(text);

var text = "Lorem ipsum dolor sit amet, consectetur adipisicing elit. Nobis dignissimos maxime et tempore omnis, ab fugit. Quos nisi, culpa exercitationem!";

console. log(text);

Works. But if there is a lot of text, we will probably have line breaks to start with new paragraph a new line. Let's try adding a line break like this to our text:

As you can see, my text editor already highlighted in red possible problem. Let's see how the browser reacts to a line break in this interpretation:

Syntax error, as expected. How to be? There are several ways to store multiline text in a variable. You might have already guessed about one of them, we're talking about about string concatenation:

As you can see, the editor already reacts normally to this option of writing a string to a variable. Another option is to use the backslash (\), which in JavaScript and many other programming languages is an escape character that allows you to safely work with special characters. We will learn what special characters are further. So let's try to screen invisible symbol line feed:

Shielding also solved our problem. However, if we look at the console, both string concatenation and line feed escaping, while solving the problem of writing to the program, did not solve the problem of displaying a multiline string on the screen. Instead of a multi-line line, we will see one-line text in the console. What should I do?

And here it will help us special character new line - \n. By adding this special character to the line in the right place, we will tell the interpreter that at this place it is necessary to end the current line and make a transition to new line.

var text = "Lorem ipsum dolor sit amet, consectetur adipisicing elit. Nobis dignissimos maxime et tempore omnis, ab fugit.\ \nQuos nisi, culpa exercitationem!"; console.log(text);

var text = "Lorem ipsum dolor sit amet, consectetur adipisicing elit. Nobis dignissimos maxime et tempore omnis, ab fugit.\

"Quos nisi, culpa exercitationem!";

console. log(text);

Actually, if you don’t mind writing the text in the code in one line, then we can do it like this:

var text = "Lorem ipsum dolor sit amet, consectetur adipisicing elit. Nobis dignissimos maxime et tempore omnis, ab fugit.\nQuos nisi, culpa exercitationem!"; console.log(text);

var text = "Lorem ipsum dolor sit amet, consectetur adipisicing elit. Nobis dignissimos maxime et tempore omnis, ab fugit.\nQuos nisi, culpa exercitationem!";

console. log(text);

The result on the screen will not change; we will see multi-line text in the browser console:

We really don’t really need the backslash escape character in the code in this situation. But it is actually needed, as noted above, for escaping special characters. For example, inside the string we enclosed in single quotes, there is an apostrophe, i.e. single quote:

var text = "Lorem ipsum d"olor sit amet";

Greetings to everyone who has thoroughly decided to learn a prototype-oriented language. Last time I told you about , and today we will parse JavaScript strings. Since in this language all text elements are strings (there is no separate format for characters), you can guess that this section occupies a significant part in learning js syntax.

That is why in this publication I will tell you how string elements are created, what methods and properties are provided for them, how to correctly convert strings, for example, convert to a number, how you can extract the desired substring and much more. In addition to this I will attach examples program code. Now let's get down to business!

String variable syntax

In the js language, all variables are declared using keyword var, and then, depending on the format of the parameters, the type of the declared variable is determined. As you remember from JavaScript, there is no strong typing. That is why this situation exists in the code.

Upon initialization variable values can be framed in double, single, and starting from 2015, in skewed single quotes. Below I have attached examples of each method of declaring strings.

I want to pay special attention to the third method. It has a number of advantages.

With its help, you can easily carry out a line break and it will look like this:

alert(`several

I'm transferring

And the third method allows you to use the $(…) construction. This tool is needed to insert interpolation. Don’t be alarmed, now I’ll tell you what it is.

Thanks to $(…) you can insert not only variable values into strings, but also perform arithmetic and logical operations with them, call methods, functions, etc. All this is called one term - interpolation. Check out an example implementation of this approach.

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var pen = 3; var pencil = 1; alert(`$(pen) + $(pencil*5) = $(pen + pencil)`);

As a result, the expression “3 + 1*5 = 8” will be displayed on the screen.

As for the first two ways of declaring strings, there is no difference in them.

Let's talk a little about special characters

Many programming languages have special characters that help manipulate text in strings. The most famous among them is line break (\n).

All similar tools initially begin with a backslash (\) and are followed by letters of the English alphabet.

Below I have attached a small table that lists some special characters.

We stock up on a heavy arsenal of methods and properties

The language developers provided many methods and properties to simplify and optimize working with strings. And with the release of a new standard called ES-2015 last year, this list was replenished with new tools.

Length

I'll start with the most popular property, which helps to find out the length of the values of string variables. This length. It is used this way:

var string = "Unicorns";

alert(string.length);

The answer will display the number 9. This property can also be applied to the values themselves:

"Unicorns".length;

The result will not change.

charAt()

This method allows you to pull out specific character from the text. Let me remind you that numbering starts from zero, so to extract the first character from a string, you need to write the following commands:

var string = "Unicorns";
alert(string.charAt(0));.

However, the resulting result will not be a character type; it will still be considered a single-letter string.

From toLowerCase() to UpperCase()

These methods control the case of characters. When writing the code "Content".

toUpperCase() the entire word will be displayed in capital letters.

For the opposite effect, you should use “Content”. toLowerCase().

indexOf()

Demanded and the right remedy to search for a substring. As an argument, you need to enter the word or phrase that you want to find, and the method returns the position of the found element. If the searched text was not found, “-1” will be returned to the user.

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var text = "Organize a flower search!"; alert(text.indexOf("color")); //19 alert(text.indexOf(" ")); //12 alert(text.lastIndexOf(" ")); //18

Note that lastIndexOf() does the same thing, only it searches from the end of the sentence.

Substring extraction

For this action, three approximately identical methods were created in js.

Let's look at it first substring (start, end) And slice (start, end). They work the same. The first argument defines the starting position from which the extraction will begin, and the second is responsible for the final stopping point. In both methods, the string is extracted without including the character that is located at the end position.

var text = "Atmosphere"; alert(text.substring(4)); // will display “sphere” alert(text.substring(2, 5)); //displays "mos" alert(text.slice(2, 5)); //display "mos"

Now let's look at the third method, which is called substr(). It also needs to include 2 arguments: start And length.

The first specifies the starting position, and the second specifies the number of characters to be extracted. To trace the differences between these three tools, I used the previous example.

var text = "Atmosphere";

alert(text.substr(2, 5)); //display "mosfe"

Using transferred funds taking substrings, you can remove unnecessary characters from new ones inline elements, with which the program then works.

Reply()

This method helps replace characters and substrings in text. It can also be used to implement global replacements, but to do this you need to include regular expressions.

This example will replace the substring in the first word only.

var text = "Atmosphere Atmosphere"; var newText = text.replace("Atmo","Strato") alert(newText) // Result: Stratosphere Atmosphere

And in this software implementation Due to the regular expression flag “g”, a global replacement will be performed.

var text = "Atmosphere Atmosphere"; var newText = text.replace(/Atmo/g,"Strato") alert(newText) // Result: Stratosphere Stratosphere

Let's do the conversion

JavaScript provides only three types of object type conversion:

Numeric;
String;
Boolean.

In the current publication I will talk about 2 of them, since knowledge about them is more necessary for working with strings.

Numeric conversion

To explicitly convert an element's value to a numeric form, you can use Number (value).

There is also a shorter expression: +"999".

var a = Number("999");

String conversion

Executed by the function alert, as well as an explicit call String(text).

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alert (999+ "super price") var text = String(999) alert(text === "999");

On this note, I decided to finish my work. Subscribe to my blog and don't forget to share the link to it with your friends. I wish you good luck in your studies. Bye bye!

Best regards, Roman Chueshov

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There are several ways to select substrings in JavaScript, including substring(), substr(), slice() and functions regexp.

In JavaScript 1.0 and 1.1, substring() exists as the only simple way to select part of a larger string. For example, to select the line press from Expression, use "Expression".substring(2,7). The first parameter to the function is the character index at which the selection begins, while the second parameter is the character index at which the selection ends (not including): substring(2,7) includes indexes 2, 3, 4, 5, and 6.

In JavaScript 1.2, functions substr(), slice() And regexp can also be used to split strings.

Substr() behaves in the same way as substr the Pearl language, where the first parameter indicates the character index at which the selection begins, while the second parameter specifies the length of the substring. To perform the same task as in the previous example, you need to use "Expression".substr(2,5). Remember, 2 is the starting point, and 5 is the length of the resulting substring.

When used on strings, slice() behaves similarly to the function substring(). It is, however, much more powerful, capable of working with any type of array, not just strings. slice() also uses negative offsets to access the desired position, starting from the end of the line. "Expression".slice(2,-3) will return the substring found between the second character and the third character from the end, returning again press.

Latest and most universal method for working with substrings - this is working through regular expression functions in JavaScript 1.2. Once again, paying attention to the same example, the substring "press" obtained from the string "Expression":

Write("Expression".match(/press/));

Built-in object String

An object String This is an object implementation of a primitive string value. Its constructor looks like:

New String( meaning?)

Here meaning any string expression that specifies the primitive value of an object. If not specified, the object's primitive value is "" .

Properties of the String object:

constructor The constructor that created the object. Number of characters per line. prototype

A reference to the object class prototype.

Standard String Object Methods Returns the character at the given position in the string. Returns the code of the character located at a given position in the string.

Returns a concatenation of strings.

Creates a string from characters specified by Unicode codes. Returns the position of the first occurrence of the specified substring. Returns the position of the last occurrence of the specified substring. Returns the position of the last occurrence of the specified substring. Returns the position of the last occurrence of the specified substring. Returns the position of the last occurrence of the specified substring. Returns the position of the last occurrence of the specified substring. Returns the position of the last occurrence of the specified substring. Compares two strings based on language Returns the position of the last occurrence of the specified substring. Returns the position of the last occurrence of the specified substring. Returns the position of the last occurrence of the specified substring. .

operating system

. : Matches a string against a regular expression. Matches a string against a regular expression and replaces the found substring with a new substring. Matches a string with a regular expression. Retrieves part of a string and returns a new string.

Splits a string into an array of substrings. length Returns a substring given by position and length.

Returns a substring specified by the starting and ending positions.

. : Matches a string against a regular expression. Converts all letters of a string to lowercase, taking into account the operating system language. Converts all letters in a string to uppercase based on the operating system language.) Converts all letters in a string to lowercase.: Converts all letters in a string to uppercase based on the operating system language. Converts an object to a string.: Converts all letters in a string to uppercase.

Returns the primitive value of the object. Non-standard methods of the String object Creates an HTML bookmark (). . There is no check to see if the original string was already enclosed in these tags. This method is used in conjunction with the document.write and document.writeln methods to create a bookmark in an HTML document with the specified name . For example, the operator document.write("My text".anchor("Bookmark")) is equivalent to the operator document.write("") .

My text

. : Matches a string against a regular expression. big method Converts an object to a string..big()

Returns the primitive value of the object. : string value big Creates an HTML bookmark (). returns a string consisting of . There is no check to see if the original string was already enclosed in these tags. This method is used in conjunction with the document.write and document.writeln methods to display text

large print

. : Matches a string against a regular expression.. For example, the statement document.write("My text".big()) will display the string My text on the browser screen. Converts an object to a string..big()

Returns the primitive value of the object. blink method.blink() Creates an HTML bookmark (). blink

returns a string consisting of a primitive string value

. : Matches a string against a regular expression.. There is no check to see if the original string was already enclosed in these tags. This method is used in conjunction with the document.write and document.writeln methods to display text in blinking font. These tags are not part of the HTML standard and are only supported by Netscape and WebTV browsers. For example, the statement document.write("My text".blink()) will display the string My text on the browser screen. Converts an object to a string..big()

Returns the primitive value of the object. bold method.blink() Creates an HTML bookmark (). .bold() bold .

.

. : Matches a string against a regular expression. There is no check to see if the original string was already enclosed in these tags. This method is used in conjunction with the document.write and document.writeln methods to display text in bold font. For example, the operator document.write("My text".bold()) will display the line My text) Converts all letters in a string to lowercase.: My text charAt method .charAt( Converts an object to a string..big()

Returns the primitive value of the object. position any numeric expression charAt Creates an HTML bookmark ( returns a string consisting of the character located in the given Matches a string against a regular expression. positions primitive string value. Line character positions are numbered from zero to

. -1. If the position is outside this range, it returns

. : Matches a string against a regular expression. empty line My text) Converts all letters in a string to lowercase.: My text. For example, the statement document.write("String".charAt(0)) will print the character C to the browser screen. Converts an object to a string.: charCodeAt method

Returns the primitive value of the object. position.charCodeAt( any numeric expression numeric value numeric expression charAt Creates an HTML bookmark ( returns a number equal to Matches a string against a regular expression. positions Unicode code symbol located in this . Line character positions are numbered from zero to NaN

.

. : Matches a string against a regular expression. For example, the statement document.write("String".charCodeAt(0).toString(16)) will display hexadecimal code, Russian letter "S": 421., , concat method) Converts all letters in a string to lowercase.: hexadecimal code, Russian letter "S": 421., , concat method.concat( Converts an object to a string..big()

Returns the primitive value of the object. line0 returns a new string that is the concatenation of the original string and the method arguments. This method is equivalent to the operation

Matches a string against a regular expression. + hexadecimal code + Russian letter "S": 421. + + concat method

For example, the operator document.write("Frost and sun.".concat("Wonderful day.")) will display the line Frost and sun on the browser screen. It's a wonderful day.

fixed method

. : Matches a string against a regular expression..fixed() Converts an object to a string..big()

Returns the primitive value of the object. fixed.blink() Creates an HTML bookmark (). .

There is no check to see if the original string was already enclosed in these tags. This method is used in conjunction with the document.write and document.writeln methods to display text in a teletype font. For example, the statement document.write("My text".fixed()) will display the string My text on the browser screen.

. : Matches a string against a regular expression. fontcolor method Converts all letters in a string to lowercase.: .fontcolor(color) color Converts an object to a string..big()

Returns the primitive value of the object. string expression.blink() Creates an HTML bookmark (). .fontcolor(color)> returns a string consisting of fontcolor specified color

. For example, the statement document.write("My text".fontcolor("red")) will display the string My text on the browser screen.

. : Matches a string against a regular expression. fontsize method .fontsize() Converts all letters in a string to lowercase.: .fontsize( size Converts an object to a string..big()

Returns the primitive value of the object. numeric expression.blink() Creates an HTML bookmark (). fontsize

.

. There is no check to see if the original string was already enclosed in these tags. This method is used in conjunction with the document.write and document.writeln methods to display text in a specified font size. For example, the statement document.write("My text".fontsize(5)) will display the string My text on the browser screen. fromCharCode method, : String.fromCharCode(, , code1) Converts all letters in a string to lowercase.: fromCharCode method, : String.fromCharCode(, , code1 code2 Converts an object to a string..big()

Returns the primitive value of the object. codeN numeric expressions fromCharCode method, : String.fromCharCode(, , code1.

fromCharCode creates a new string (but not a string object) that is the concatenation of Unicode characters with codes This String static method

object

, so you don't need to specifically create a string object to access it. Example:

. : Matches a string against a regular expression. Var s = String.fromCharCode(65, 66, 67); // s equals "ABC" indexOf method[,.indexOf(]?) Converts all letters in a string to lowercase.: indexOf method substring .indexOf(. For example, the statement document.write("String".charAt(0)) will print the character C to the browser screen. Converts an object to a string. Start

Returns the primitive value of the object. any string expression: numeric value indexOf returns first position Creates an HTML bookmark (. Matches a string against a regular expression. .indexOf( .indexOf( .indexOf( .indexOf( substrings Matches a string against a regular expression. Matches a string against a regular expression.

in a primitive string value

more than

The search is carried out from left to right. Otherwise, this method is identical to the method.

. : Matches a string against a regular expression. The following example counts the number of occurrences of the substring pattern in the string str . Converts an object to a string..big()

Returns the primitive value of the object. Function occur(str, pattern) ( var pos = str.indexOf(pattern); for (var count = 0; pos != -1; count++) pos = str.indexOf(pattern, pos + pattern.length); return count ; ).blink() Creates an HTML bookmark (). Italics method bold .

.italics()

. : Matches a string against a regular expression. italics indexOf method[,.indexOf(]?) Converts all letters in a string to lowercase.: indexOf method substring .indexOf(. For example, the statement document.write("String".charAt(0)) will print the character C to the browser screen. Converts an object to a string. Start

Returns the primitive value of the object. . There is no check to see if the original string was already enclosed in these tags. This method is used in conjunction with the document.write and document.writeln methods to display text in italic font. For example, the operator document.write("My text".italics()) will display the line indexOf in the primitive string value Creates an HTML bookmark ( Matches a string against a regular expression.. -1. If an optional argument is given .indexOf(, then the search is carried out starting from the position .indexOf(; .indexOf( if not, then from position 0, i.e. from the first character of the line. If negative, then it is accepted equal to zero .indexOf( substrings Matches a string against a regular expression.; If Matches a string against a regular expression.. -1, then it is taken equal

. -1. If the object does not contain this substring, then the value -1 is returned.

The search is carried out from right to left. Otherwise, this method is identical to the method.

Example:

. : Matches a string against a regular expression. Var n = "White whale".lastIndexOf("whale"); // n equals 6 link method) Converts all letters in a string to lowercase.: link method.link( Converts an object to a string..big()

Returns the primitive value of the object. uri.blink() Creates an HTML bookmark ( any string expression link link method, enclosed in uri tags

"> . There is no check to see if the source string was already enclosed within these tags. This method is used in conjunction with the document.write and document.writeln methods to create a hyperlink in an HTML document with the specified

. : Matches a string against a regular expression.. For example, the statement document.write("My Text".link("#Bookmark")) is equivalent to the statement document.write("My Text") . Russian letter "S": 421.) Converts all letters in a string to lowercase.: Russian letter "S": 421..link( Converts an object to a string. localeCompare method

.localeCompare(

Returns the primitive value of the object. : number Support Creates an HTML bookmark ( localeCompare compares two strings taking into account the national settings of the operating system. It returns -1 if primitive value less compares two strings taking into account the national settings of the operating system. It returns -1 if primitive value lines1

, +1 if it is greater

. : Matches a string against a regular expression., and 0 if these values are the same. match method) Converts all letters in a string to lowercase.: match method Converts an object to a string..match(

Returns the primitive value of the object. regvyr match method Creates an HTML bookmark (: array of strings match. The result of the match is an array of found substrings or

null match method, if there are no matches. Wherein: If does not contain an option match method.global search(Matches a string against a regular expression., then the method is executed match method exec ) and its result is returned. The resulting array contains the found substring in the element with index 0, and the remaining elements contain substrings corresponding to the subexpressions.
null match method, enclosed in match method.global search(Matches a string against a regular expression. round brackets match method.contains a global search option, then the method) is executed as long as matches are found. If n is the number of matches found, then the result is an array of n elements that contain the found substrings. Property

lastIndex match method.global search assigned a position number in the source string pointing to the first character after the last match found, or 0 if no matches were found. match method It should be remembered that the method

changes object properties

. : Matches a string against a regular expression.. Examples: match method,replace method) Matches a string against a regular expression.. Examples: match method,.replace() Converts all letters in a string to lowercase.: match method line .replace( function Converts an object to a string. regular expression string string expression

Returns the primitive value of the object. function name or function declaration: new line match method replace Creates an HTML bookmark ( and replaces the found substrings with other substrings. The result is a new string, which is a copy of the original string with the replacements made. The replacement method is determined by the global search option in match method and the type of the second argument.

null match method does not contain a global search option, then the search is performed for the first substring that matches match method and it is replaced. match method If match method contains a global search option, then all substrings matching

replace method, and they are replaced. , then each found substring is replaced with it. In this case, the line may contain the following object properties RegExp

, like $1 , , $9 , lastMatch , lastParen , leftContext and rightContext . .replace( For example, the operator document.write("Delicious apples, juicy apples.".replace(/apples/g, "pears")) will display the line Delicious pears, juicy pears on the browser screen. match method If the second argument is function name or function declaration, then each substring found is replaced by calling this function. The function has the following arguments. The first argument is the found substring, followed by arguments matching all subexpressions

, enclosed in parentheses, the penultimate argument is the position of the found substring in the source string, counting from zero, and the last argument is the source string itself. The following example shows how to use the method

you can write a function to convert Fahrenheit to Celsius. The given scenario

Function myfunc($0,$1) ( return (($1-32) * 5 / 9) + "C"; ) function f2c(x) ( var s = String(x); return s.replace(/(\d+( \.\d*)?)F\b/, myfunc); ) document.write(f2c("212F")); match method.

will display the line 100C on the browser screen.

Please note that this method changes the properties of the object

Replace example

Replacing all occurrences of a substring in a string

It often happens that you need to replace all occurrences of one string with another string:

. : Matches a string against a regular expression. Var str = "foobarfoobar"; str=str.replace(/foo/g,"xxx"); // the result will be str = "xxxbarxxxbar"; match method) Converts all letters in a string to lowercase.: match method search method Converts an object to a string..search(

Returns the primitive value of the object. any regular expression: new line match method replace Creates an HTML bookmark (: numeric expression match method search match method. The result of the match is the position of the first substring found, counting from zero, or -1 if there are no matches. At the same time, the global search option in

is ignored, and properties

. : Matches a string against a regular expression. do not change. .indexOf( [,Examples:]?) Converts all letters in a string to lowercase.: .indexOf( And Examples: slice method Converts an object to a string. regular expression string string expression

Returns the primitive value of the object. .slice( Creates an HTML bookmark ( end .indexOf( any numerical expressions Examples: slice Examples: .indexOf(, from position

to position Matches a string against a regular expression., without including it. If .indexOf( Matches a string against a regular expression.. +.indexOf( and until the end of the original line. Examples: Line character positions are numbered from zero to Matches a string against a regular expression.. +Examples:.

In other words, negative arguments are treated as offsets from the end of the string.

The result is a string value, not a string object. For example, the statement document.write("ABCDEF".slice(2,-1)) will print the string CDE to the browser screen.

. : Matches a string against a regular expression. small method Converts an object to a string..big()

Returns the primitive value of the object. .small().blink() Creates an HTML bookmark (). small

.

. : Matches a string against a regular expression. There is no check to see if the original string was already enclosed in these tags. This method is used in conjunction with the document.write and document.writeln methods to display text in small font. For example, the statement document.write("My text".small()) will display the string My text on the browser screen. split method [,.split(]?) Converts all letters in a string to lowercase.: split method delimiter .split( size Converts an object to a string. number string or regular expression)

Returns the primitive value of the object. : string array(object Array Creates an HTML bookmark ( split breaks the primitive value to an array of substrings and returns it. The division into substrings is done as follows. The source string is scanned from left to right looking for

delimiter .split(. Once it is found, the substring from the end of the previous delimiter (or from the beginning of the line if this is the first occurrence of the delimiter) to the beginning of the one found is added to the substring array. Thus, the separator itself does not appear in the text of the substring. Optional argument sets the maximum possible size the resulting array. If it is specified, then after selection

numbers The substring method exits even if the scan of the original string is not finished.

Delimiter

can be specified either as a string or as a regular expression. There are several cases that require special consideration:

The following example uses a regular expression to specify HTML tags as a delimiter. Operator

. : Matches a string against a regular expression. will display the line Text, bold, and italic on the browser screen. Converts an object to a string..big()

Returns the primitive value of the object. strike method.blink() Creates an HTML bookmark (). .strike()

strike

. : Matches a string against a regular expression.. Converts an object to a string..big()

Returns the primitive value of the object. There is no check to see if the original string was already enclosed in these tags. This method is used in conjunction with the document.write and document.writeln methods to display text in a strikethrough font. For example, the statement document.write("My text".strike()) will display the string My text on the browser screen..blink() Creates an HTML bookmark (). sub method

.sub()

. : Matches a string against a regular expression. sub My text [,.]?) Converts all letters in a string to lowercase.: My text And . code2 Converts an object to a string..big()

Returns the primitive value of the object. substr There is no check to see if the original string was already enclosed in these tags. This method is used in conjunction with the document.write and document.writeln methods to display text as a subscript. For example, the statement document.write("My text".sub()) will display the string My text on the browser screen. Creates an HTML bookmark ( substr method numeric expression.substr( . length . is not specified, then a substring is returned starting from the given one numeric expression and until the end of the original line. If . is negative or zero, an empty string is returned.

to position Matches a string against a regular expression.. -1. If My text greater than or equal to Matches a string against a regular expression.., then an empty string is returned. If My text is negative, then it is interpreted as an offset from the end of the line, i.e., it is replaced by Matches a string against a regular expression..+My text.

Note. If My text is negative, then Internet Explorer mistakenly replaces it with 0, so for compatibility reasons this option should not be used.

Var src = "abcdef"; var s1 = src.substr(1, 3); // "bcd" var s2 = src.substr(1); // "bcdef" var s3 = src.substr(-1); // "f", but in MSIE: "abcdef"

substring method

. : Matches a string against a regular expression..substring( .indexOf( [,Examples:]) Converts all letters in a string to lowercase.: .indexOf( And Examples: code2 Converts an object to a string..big()

Returns the primitive value of the object. substring There is no check to see if the original string was already enclosed in these tags. This method is used in conjunction with the document.write and document.writeln methods to display text as a subscript. For example, the statement document.write("My text".sub()) will display the string My text on the browser screen. Creates an HTML bookmark ( end .indexOf( any numerical expressions Examples: slice Examples: is not specified, then a substring is returned, starting from position .indexOf(, from position

to position Matches a string against a regular expression.. -1. Negative arguments or equal Unicode code are replaced by zero; if the argument is greater than the length of the original string, then it is replaced with it. If .indexOf( more end, then they change places. If .indexOf( equals end, then an empty string is returned.

The result is a string value, not a string object. Examples:

Var src = "abcdef"; var s1 = src.substring(1, 3); // "bc" var s2 = src.substring(1, -1); // "a" var s3 = src.substring(-1, 1); // "a"

sup method

. : Matches a string against a regular expression..sup() Converts an object to a string..big()

Returns the primitive value of the object. sup.blink() Creates an HTML bookmark (). .

There is no check to see if the original string was already enclosed in these tags. This method is used in conjunction with the document.write and document.writeln methods to display text as a superscript. For example, the statement document.write("My text".sup()) will display the string My text on the browser screen.

. : Matches a string against a regular expression. toLocaleLowerCase Method Converts an object to a string..toLocaleLowerCase()

.localeCompare(: new line

Returns the primitive value of the object. : Internet Explorer Supported from version 5.5. Netscape Navigator Not supported. toLocaleLowerCase

returns a new string in which all letters of the original string are replaced with lowercase ones, taking into account the locale settings of the operating system. The remaining characters of the original string are not changed. The original string remains the same. Typically this method returns the same result as ; the difference is only possible if the language encoding conflicts with the Unicode rules for converting uppercase to lowercase letters.

. : Matches a string against a regular expression. toLocaleUpperCase Method Converts an object to a string..toLocaleLowerCase()

.localeCompare(: new line

Returns the primitive value of the object. .toLocaleUpperCase() returns a new string in which all letters of the original string are replaced with uppercase, taking into account the locale settings of the operating system. The remaining characters of the original string are not changed. The original string remains the same. Typically this method returns the same result as ; the difference is only possible if the language encoding conflicts with the Unicode rules for converting lowercase letters to uppercase letters.

toLowerCase method

. : Matches a string against a regular expression..toLowerCase() Converts an object to a string. regular expression string string expression

Returns the primitive value of the object. toLowerCase returns a new string with all letters of the original string replaced with lowercase ones. The remaining characters of the original string are not changed. The original string remains the same. For example, the statement document.write("String object".toLowerCase()) will print the string object string to the browser screen.

As semantic “frameworks” for the use of functions and constructions for processing strings, they are of particular interest for programming information processing processes according to its semantic content. On JavaScript functions for working with strings can be combined into their own semantic constructs, simplifying the code and formalizing subject area tasks.

In the classical version, information processing is primarily string functions. Each function and construct of the language has its own characteristics in the syntax and semantics of JavaScript. The methods for working with strings here have their own style, but in common use it is just syntax within simple semantics: search, replace, insertion, extraction, connotation, change case...

Description of string variables

To declare a string, use the construction var. You can immediately set its value or generate it during the execution of the algorithm. You can use single or double quotes for a string. If it must contain a quotation mark, it must be escaped with the "\" character.

The line indicated requires escaping internal double quotes. Likewise, the one marked with single quotes is critical to the presence of single quotes inside.

IN in this example the string "str_dbl" lists useful special characters that can be used in the string. In this case, the “\” character itself is escaped.

A string is always an array

JavaScript can work with strings in a variety of ways. The language syntax provides many options. First of all, one should never forget that (in the context of the descriptions made):

str_isV => "V";
str_chr => """;
str_dbl => "a".

That is, the characters in a string are available as array elements, with each special character being one character. Escaping is an element of syntax. No “screen” is placed on the actual line.

Using the charAt() function has a similar effect:

str_isV.charAt(3) => "V";
str_chr.charAt(1) => """;
str_dbl.charAt(5) => “a”.

The programmer can use any option.

Basic String Functions

In JavaScript it is done a little differently than in other languages. The name of the variable (or the string itself) is followed by the name of the function, separated by a dot. Typically, string functions are called methods in the style of language syntax, but the first word is more familiar.

The most important method of a string (more correctly, a property) is its length.

var xStr = str_isV.length + "/" + str_chr.length + "/" + str_dbl.length.

Result: 11/12/175 according to the lines of the above description.

The most important pair of string functions is splitting a string into an array of elements and merging the array into a string:

split(s [, l]);
join(s).

In the first case, the string is split at the delimiter character “s” into an array of elements in which the number of elements does not exceed the value “l”. If the quantity is not specified, the entire line is broken.

In the second case, the array of elements is merged into one line through a given delimiter.

A notable feature of this pair: splitting can be done using one separator, and merging can be done using another. In this context in JavaScript work with strings can be "taken outside" the syntax of the language.

Classic string functions

Common string processing functions:

search;
sample;
replacement;
transformation.

Represented by methods: indexOf(), lastIndexOf(), toLowerCase(), toUpperCase(), concan(), charCodeAt() and others.

In JavaScript, working with strings is represented by a large variety of functions, but they either duplicate each other or are left for old algorithms and compatibility.

For example, using the concat() method is acceptable, but it is easier to write:

str = str1 + str2 + str3;

Using the charAt() function also makes sense, but using charCodeAt() has real practical meaning. Similarly, for JavaScript, a line break has a special meaning: in the context of displaying, for example, in an alert() message, it is “\n”, in a page content generation construct it is “
" In the first case it is just a character, and in the second it is a string of characters.

Strings and Regular Expressions

In JavaScript, working with strings includes a mechanism regular expressions. This allows complex searches, fetching, and string conversions to be performed within the browser without contacting the server.

Returns the primitive value of the object. regvyr finds, and function name or function declaration replaces the found match with the desired value. Regular expressions are implemented in JavaScript in high level, in essence, are complex, and due to the specifics of the application, they transfer the center of gravity from the server to the client’s browser.

When applying methods match, search And replace You should not only pay due attention to testing over the entire range of acceptable values of the initial parameters and search strings, but also evaluate the load on the browser.

Regular expression examples

The scope of regular expressions for processing strings is extensive, but requires great care and attention from the developer. First of all, regular expressions are used when testing user input in form fields.

Here are functions that check whether the input contains an integer (schInt) or a real number (schReal). The following example shows how efficient it is to process strings by checking them for only valid characters: schText - text only, schMail - correct address Email.

It is very important to keep in mind that in JavaScript, characters and strings require increased attention to locale, especially when you need to work with Cyrillic. In many cases, it is advisable to specify the actual character codes rather than their meanings. This applies primarily to Russian letters.

It should be especially noted that it is not always necessary to complete the task as it is set. In particular, with regard to checking integers and real numbers: you can get by not with classic string methods, but with ordinary syntax constructions.

Object-Oriented Strings

In JavaScript, working with strings is represented by a wide range of functions. But this is not a good reason to use them in their original form. The syntax and quality of the functions are impeccable, but it is a one-size-fits-all solution.

Any use of string functions involves processing the real meaning, which is determined by the data, the scope of application, and the specific purpose of the algorithm.

The ideal solution is always to interpret data for its meaning.

By representing each parameter as an object, you can formulate functions to work with it. We are always talking about processing symbols: numbers or strings are sequences of symbols organized in a specific way.

Eat general algorithms, and there are private ones. For example, a surname or house number are strings, but if in the first case only Russian letters are allowed, then in the second case numbers, Russian letters are allowed, and there may be hyphens or indices separated by a slash. Indexes can be alphabetic or numeric. The house may have buildings.

It is not always possible to foresee all situations. This important point in programming. It is rare that an algorithm does not require modification, and in most cases it is necessary to systematically adjust the functionality.

Formalization of the processed line information in the form of an object improves the readability of the code and allows it to be brought to the level of semantic processing. This is a different degree of functionality and significantly best quality code with greater reliability of the developed algorithm.