Regular Expressions (replacements)//References

The syntax for the Replace method is: Stringobj.replace (rgexp, ReplaceText) where Stringobj is a string (string), Reexp can be a regular expression object (REGEXP) or it can be a string ( String), ReplaceText is the alternative to finding the string: To help you understand better, here's a simple example to illustrate

JS Code

1.    <script language= "JavaScript" >   2.    var stringobj= "The end of the ancient People's Republic, the end of the ancient people";   3.      4.    Replace the typo "end ancient" for "China"   5.    and returns the new character 6 after replacement   .    The value of the original string stringobj has not changed by   7.    var newstr=stringobj.replace ("End Ancient", "China");   8.    alert (NEWSTR);   9.    </script>  

　　

The end of the ancient "for China"

The value has not changed

China ");

You are smarter than me, after reading the above example, you will find that the second typo "end ancient" has not been replaced with "China", we can execute two times replace method to replace the second typo "End Ancient", the program has been improved as follows:

JS Code

1.    <script language= "JavaScript" >   2.    var stringobj= "The end of the ancient People's Republic, the end of the ancient people";   3.      4.    Replace the typo "end ancient" for "China"   5.    and returns the new character 6 after replacement   .    The value of the original string stringobj has not changed by   7.    var newstr=stringobj.replace ("End Ancient", "China");   8.      9.    Newstr=newstr.replace ("End Ancient", "China");   alert (NEWSTR);   One. </script>  

　　

The end of the ancient "for China"

The value has not changed

China ");

China ");

We can carefully think about, if there is N of the N-square typos, is not also to execute n the N-square replace method to replace the typos?? Oh, don't be afraid, with a regular expression after the use of a typo to perform a replace method. The code after the program has been improved is as follows

JS Code

1.    <script language= "JavaScript" >   2.    var reg=new RegExp ("End Ancient", "G"); Create the regular RegExp object   3.    var stringobj= "The end of the ancient People's Republic, the end of the ancient people";   4.    var newstr=stringobj.replace (Reg, "China");   5.    alert (NEWSTR);   6.    </script>  

　　

Create a regular RegExp object

Above is the Replace method of the simplest application, do not know if you understand?? Let's start with a slightly more complex application.


When you search for articles on some websites, you will find this phenomenon, that is, the search keywords will be highlighted to change the color display?? How is this achieved?? In fact, we can use regular expressions to achieve, specifically how to achieve it? See the following code for a simple principle

JS Code

The above program is lack of interactivity, we can improve the program, to achieve the self-input to find the character

JS Code

1. <script language= "JavaScript" >

2. var s=prompt ("please

1.    <script language= "JavaScript" >   2.    var str= "People's Republic of China";   3.    var newstr=str.replace (/(person)/g, "<font color=red>$1</font>");   4.    document.write (NEWSTR);   5.    </script>  

　　

Enter the characters in the find "," person ");

3.    var reg=new RegExp ("(" +s+ ")", "G");   4.    var str= "People's Republic of China, People's Republic of China";   5.    var newstr=str.replace (Reg, "<font color=red>$1</font>");   6.    document.write (NEWSTR);   7.    </script>

　　

People ");

It may be that everyone will be able to express what the meaning of the special character is not very understanding, in fact, is the expression in the left side of the parentheses in the character, that is, the first sub-match, the same can be a second sub-match: What is a sub-match?? Popular point, is the left each parenthesis is the first word match, the second parenthesis is the second sub-match:


How do we do this when we are going to do the arithmetic of the found character?? Before we do that, let's talk about how to get the arguments for a function: Within function functions, there is a arguments collection, which stores all the parameters of the current function, and through arguments can get all the parameters of the function, for your understanding, see the following code

JS Code

1.    <script language= "JavaScript" >   2.    function test () {   3.       Alert ("Number of parameters:" +arguments.length);   4.       alert ("value of each parameter:" +arguments[0]);   5.       alert ("The value of the second parameter" +arguments[1]);   6.      //can read all parameters with a for loop   7.    }   8.      9.    Test ("AA", "BB", "cc");   </script> alert ("Alert" ("  Alert"///Loop all parameters

　　

After reading the above procedure, let's take a look at the following interesting program

JS Code

1.    <script language= "JavaScript" >   2.    var reg=new RegExp ("\\d", "G");   3.    var str= "ABD1AFA4SDF";   4.    str.replace (reg,function () {alert (arguments.length);});   5.    </script>  

　　

Regular Expressions (replacements)//References