The role of parameter g (global) in javascript regular expressions

The role of parameter g (global) in javascript regular expressions_javascript skills

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Release： 2016-05-16 18:16:27

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We describe in detail:
1) For the exec method of the expression object, if g is not added, only the first match will be returned, no matter how many times it is executed. If g is added, the first match will be returned for the first time. match, then perform the second match, and so on. For example:

Copy code The code is as follows:

 
var regx=/userd/; 
 var str="user18duser2dsc"; 
var rs=regx.exec(str);//The value of rs at this time is {user1} 
var rs2=regx.exec(str);//The value of rs at this time The value is still {user1} 

If regx=/userd/g:, then the value of rs is {user1} and the value of rs2 is {user2}

Explain through this example: For the exec method, g is added to the expression. It does not mean that all matches can be returned by executing the exec method, but that after g is added, all matches can be obtained in a certain way. The "method" here is for exec , just execute this method.
2) For the test method of the expression object, there is no difference between adding g and not adding g.
3) For the match method of the String object, if g is not added, it will only return the first match. If the match method is always executed, the first match will always be returned. If g is added, all matches will be returned at once. For example:

Copy code The code is as follows:

 
var regx=/userd/; 
 var str="user1dge3user2gwe"; 
var rs=str.match(regx);//The value of rs at this time is {user1} 
var rs2=str.match(regx);//The value of rs2 at this time The value is still {user1} 

If regx=/userd/g, then the value of rs is {user1, user2}, and the value of rs2 is also {user1, user2}

4) For the replace method of the string object, if g is not added to the expression, only the first match will be replaced. If g is added, all matches will be replaced.

5) For the split method of String object, adding g is the same as not adding g, that is:

Copy code The code is as follows:

 
var sep=/userd/; 
var array=”user1dfsfuser2dfsf”.split(sep); 

Then array is The value is {dfsf,dfsf}. When sep=/userd/g, the return value is the same.

6) For the search method of the string object, it is the same whether or not g is added.