javascript regular expression trigger function for advanced replacement_javascript skills

Under normal circumstances, we may use regular expressions to replace text:

Copy code The code is as follows:

var a = "abc123aXc";
a.replace(/a.c/g, 'ZZ');

We can use functions to define advanced replacements instead of a simple string. For example:

<div class="codetitle"> [/code] The execution result is: <span><a style="CURSOR: pointer" data="20953" class="copybut" id="copybut20953" onclick="doCopy('code20953')"><u></u>Copy code</a></span> </div> The code is as follows:<div class="codebody" id="code20953"> www 15bj ten <br><input onclick="runEx('runcode15507')" type="button" value="运行代码"><input onclick="doCopy('runcode15507')" type="button" value="复制代码"> <input onclick="doSave(runcode15507)" type="button" value="保存代码"> <a href="http://www.jb51.net/article/23421.htm" title="查看具体详情" target="_blank">[Ctrl A Select all Note: </a>If you need to introduce external Js, you need to refresh to execute </div>]<br> <br>We see that when the regular Each time the expression generates a match, the replacement function is triggered and the matching string is passed as a parameter to the replacement function. When a submatch is defined in the regular expression, you can even do more advanced things, and the replacement function can perform corresponding processing according to different submatches. For example, we want to convert some specified entity codes in the web page into special characters: <br>[code] <br>var entity = { <br>quot: '"', <br>lt: '<', <BR>gt: '>' <br>}; <br>function deentityify(a, b) { <br>var r = entity[b]; <br>return typeof r === 'string' ? r : a; <br>} <br>var a = "<a href="http://jb51.net/">"; <br>a.replace(/&([^&;] ); /g, deentityify);

The execution result is:


If we know the delivery The principle of the parameter rules will be very clear. In fact, if a submatch is defined in the regular expression, the length of the parameter will change with the number of submatches. If no submatch is defined, the length is fixed. . The rules for passing parameters are:

Matches the string itself
All submatches (if defined) <script> function reverseMatch(str) { return str.split('').reverse().join(''); } var a = "www jb51 net"; a=a.replace(/\w+/g, reverseMatch); alert(a); </script> Matches the position of the string in the original string