JS replaces the specified character _ regular expression with the replacement of the regular with the replace

Definitions and Usage

The replace () method replaces some characters in a string with some other characters, or replaces a substring that matches a regular expression.

Grammar

Stringobject.replace (regexp,replacement)

Parameter description
RegExp required. The RegExp object that sets the pattern to be replaced. Note that if the value is a string, it is used as the direct text pattern to retrieve, not first converted to the RegExp object.
Replacement required. A string value. Provides a function that replaces text or generates alternate text.

return value

A new string that is replaced with replacement for the first match of RegExp or after all matches have been made.

Description

The replace () method of the string Stringobject performs a find-and-replace operation. It will look for substrings in the stringobject that match the regexp, and then replace them with replacement. If RegExp has global flag G, then the Replace () method replaces all matching substrings. Otherwise, it replaces only the first matching substring.

Replacement can be either a string or a function. If it is a string, then no match will be replaced by the string. However, the $ character in replacement has a specific meaning. As shown in the following table, it shows that the string that is matched from the pattern will be used for substitution.
Character replacement text
$ 、...、 $99 The text that matches the 1th to 99th subexpression in the RegExp.
$& the substring that matches the regexp.
$ ' is the text on the left side of the matching substring.
$ ' is the text on the right side of the matching substring.
% direct measure symbol.

Note: The ECMAScript v3 stipulates that the parameter replacement of the replace () method can be a function rather than a string. In this case, each match calls the function, and the string it returns is used as the replacement text. The first parameter of the function is a string that matches the pattern. The next argument is a string that matches the subexpression in the pattern, and can have 0 or more of these parameters. The next argument is an integer that declares where the match appears in the Stringobject. The last parameter is the stringobject itself.

instance

Example 1

In this case, we'll use "w3school" to replace "Microsoft" in the string:

Copy Code code as follows:

<script type= "Text/javascript" >

var str= "Visit microsoft!"
document.write (Str.replace (/microsoft/, "W3school"))

</script>

Output:

Visit w3school!

Example 2

In this case, we will perform a global substitution, which is replaced with "W3school" whenever "Microsoft" is found:

Copy Code code as follows:

<script type= "Text/javascript" >

var str= "Welcome to microsoft! "
Str=str + "We are proud to announce" Microsoft has "
Str=str + "One of the" largest WEB developers sites in the world. "

document.write (Str.replace (/microsoft/g, "W3school"))

</script>

Output:

Welcome to w3school! We are proud to announce that W3school
has one of the largest WEB developers sites in the world.

Example 3

You can use the code provided in this example to ensure that matching string uppercase characters are correct:

Copy Code code as follows:

Text = "JavaScript Tutorial";
Text.replace (/javascript/i, "JavaScript");

Example 4

In this case, we'll convert "Doe, John," to "John Doe" in the form of:

Copy Code code as follows:

Name = "Doe, John";
Name.replace (/(\w+) \s*, \s* (\w+)/, "$ $");

Example 5

In this case, we'll replace all the curly quotes with straight quotes:

Copy Code code as follows:

Name = ' "A", "B";
Name.replace ([^ "]*)"/g, "' $ '");

Example 6

In this case, we will convert the first letter of all words in the string to uppercase:

Copy Code code as follows:

Name = ' AAA bbb CCC ';
Uw=name.replace (/\b\w+\b/g, function (word) {
Return word.substring (0,1). toUpperCase () +word.substring (1);}
);

Example 7

Copy Code code as follows:

var str= "FSAF$A$ASSDFDASFA$A$DSFADSF";
var strr= ' \$ ' + ' a ' + ' \$ ';
var name = ' A ', ' B ';
var reger=new RegExp ("[\$]a[\$]", "GM");

Alert (str.replace (Reger, ' 555888 '));

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