The second parameter of JavaScript replace() is the function:
The replace() function has a replacement function. It can have two parameters. The first parameter can be a string to be replaced or a regular expression matching the string to be replaced. The second parameter can be a text or a function. Let's take a look at several code examples about the replace() function.
Code example:
Example 1:
<script>
var str="I love jb51 and you?";
(("jb","java"));
</script>
The above code can only replace the first specified substring in the string.
Example 2:
<script> var str="I love jb51 and you?"; var reg=/jb/g; ((reg,"java")); </script>
The above code can replace all specified substrings in the string.
Example 3:
<script>
var str="I love jb51 and you?";
(("jb",function(){
return "java"}
));
</script>
In the above code, the second parameter is a function that can replace the specified substring in the string with the return value of this function. When the second parameter is a function, this function can actually pass parameters. Let’s introduce the parameter issue about the function through code examples.
The code is as follows:
<!DOCTYPE html>
<html>
<head>
<meta charset=" utf-8">
<title>I</title>
<script type="text/javascript">
var url = "https:///?mod=viewthread&tid=14743&extra=page%3D1";
//The first parameter is a string("String");
var oneResult = ("",function(){
("replace input parameter: %o",arguments);
var val = //.exec(url);
("exec output parameter: %o",val);
(arguments[0] === val[0]);
(arguments[1] === val["index"]);
(arguments[2] === val["input"]);
return "jb51";
});
("replace returns string:"+oneResult);
("String");
//The first parameter is a regular expression("regular expression");
var regexp_global = /[?&](\w+)=([^&]*)/g;
var count = 0;
var twoResult = (regexp_global,function(){
("Third"+(count++)+"Second run");
("replace input parameter: %o",arguments);
var val = regexp_global.exec(url);
("exec output parameter: %o",val);
(arguments[0] === val[0]);
(arguments[1] === val[1]);
(arguments[2] === val[2]);
(arguments[3] === val["index"]);
(arguments[4] === val["input"]);
return count;
});
("replace returns string:"+twoResult);
("regular expression");
</script>
</head>
<body>
</body>
</html>
In the above code, we demonstrate the situation when the first parameter of the replace() function is a normal string and a regular expression, and the second function parameter is passed. Here are some simple explanations:
The first parameter is a normal string:
When the first parameter is a normal string, it will only replace the first substring in the original string, which means that only one substring will be performed. The parameters passed for the function are the same as the elements of the array returned by the exec() function using the normal string parameters as regular expressions.
The first parameter is the regular expression:
Due to space reasons, only part of the running result is intercepted. The first parameter of the replace() function is a regular expression and the execution of a global match. Then the second function parameter will be called many times. The parameters passed each time are the same as the element content of the array returned by regexp_global.exec(url).