Search for and replace Javascript strings

In js, We need to search for strings and use indexOf and then replace (). In fact, we don't need to do this at all. We just need a simple positive table expression under replace.

The replace (regexp, replacement) method has two parameters. The first parameter can be a plain text string or a RegExp object. For details, see the use of the RegExp object; the second parameter can be a string or a function.

The following is an example of JS string replacement:

If it is a normal replacement, you can only Replace the first one. To replace all, you must use a regular expression. The following code shows the differences between the two:

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<Html> <Head> <Title> test </title> <Script language = "JavaScript"> <! -- Var s = "testtest ";   // G in the second parameter indicates that all matches, And I indicates that case-insensitive Var regS = new RegExp ("test", "gi ");   Alert (s. replace ("test", "Hello"); // replace only one Alert (s. replace (regS, "Hello"); // replace all // --> </Script> </Head> <Body> </Body> </Html>

Next let's look at the instance

Example 1:

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Var str = "Hello world! "; Document. write (str. replace (/world/, "phper "));

Example 2:

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Var reg = new RegExp ("(\ w +), (\ d +), (\ w +)", "gmi "); Var info = "Lili, 14, China "; Var rep = info. replace (reg, "She is $1, $2 years old, come from $3 "); Alert (rep );

Example 3:

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Var reg = new RegExp ("(\ w +), (\ d +), (\ w +)", "gmi "); Var info = "Lili, 14, China "; Var name, age, from; Function prase_info (m, p1, p2, p3) {// you can also use a non-explicit parameter, obtained using arguments Name = p1; Age = p2; From = p3; Return "She is" + p1 + "," + p2 + "years old, come from" + p3; } Var rep = info. replace (reg, prase_info ); Alert (rep ); Aler (name );

2. Use of RegExp objects

JavaScript provides a RegExp object to perform operations and functions on regular expressions. Each regular expression pattern corresponds to a RegExp instance. You can create an instance of the RegExp object in two ways.

Use RegExp's explicit constructor Syntax: new RegExp ("pattern" [, "flags"]); Use RegExp's implicit constructor in plain text format: /pattern/[flags]. In Example 4, the two statements are equivalent.

Example 4:

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Var re1 = new RegExp ("\ d {5 }"); Var re2 =/d {5 }/;

3. string search and use of the exec () method

The exec () method returns an array containing matching results. If no match is found, the return value is null.

Example 5:

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Var reg = new RegExp ("(\ w +), (\ d +), (\ w +)", "gmi "); Var m1_reg.exe c ("Lili, 14, China "); Var s = ""; For (I = 0; I <m. length; I ++ ){ S = s + m [I] + "n "; } Alert (s );

4. Use of the test () method

RegExpObject. test (string)

If the string contains the text that matches RegExpObject, true is returned; otherwise, false is returned.

Example 6:

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Var reg = new RegExp ("(\ w +), (\ d +), (\ w +)", "gmi "); Var m = reg. test ("Lili, 14, China "); Alert (RegExp. $1 ); Alert (RegExp. $2 ); Alert (RegExp. $3 );

Add the js replacement method.

The return value is the string after the replacement operation is executed.

String. replace ()
 

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Var text = "javascript is very powerful! "; Text. replace (/javascript/I, "JavaScript ");

// Return: JavaScript is very powerful!
String. replace () replace all Target Characters
 

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Var text = "javascript is very powerful! JAVASCRIPT is my favorite language! "; Text. replace (/javascript/ig, "JavaScript "); // Return: JavaScript is very powerful! JavaScript is my favorite language!

String. replace ()
 

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Var name = "Doe, John "; Name. replace (/(w +) s *, s * (w +)/, "$2 $1 "); // Return value: John Doe

String. replace () is used to replace all characters in double quotation marks with characters in brackets.
 

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Var text = '"JavaScript" is very powerful! '; Text. replace (/"([^"] *) "/g," [$1] "); // Return: [JavaScript] is very powerful!

String. replace () uppercase letters
 

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Var text = 'a journey of a thousand miles begins with single step .'; Text. replace (/bw + B/g, function (word ){ Return word. substring (0, 1). toUpperCase () + Word. substring (1 ); });   // Return: A Journey Of A Thousand Miles Begins With Single Step.