Description of the difference between the JavaScript regular expression exec () and match ()

This article is mainly on the JS regular expression exec and match the difference between the introduction, the need for friends can come to the reference, I hope to help you.

Regular expression rules some rules are no longer stated here, only the difference between exec and match is recorded:

1, Exec is the method of the regular expression, not the method of the string, its parameter is the string, as follows:

As defined above
var reg = new RegExp ("abc");
var str = "3ABC4,5ABC6";
Reg.exec (str);

2. Match is a string that performs a method of matching regular expression rules, and his arguments are regular expressions, such as

var reg = new RegExp ("abc");
var str = "3ABC4,5ABC6";
Str.match (REG);

3, exec and match return are arrays;

If the regular expression executed by Exec does not have a subexpression (the contents of parentheses, such as/ABC (\s*)/(\s*)), if there is a match, returns the first matched string content, at which point the array has only one element, and if no match returns null;

var reg = new RegExp ("abc");
var str = "3ABC4,5ABC6";
Alert (reg.exec (str));
Alert (Str.match (reg));

Execute the above code, and you'll see that both things are the same: ABC,

4. If you define a regular expression object as a global match, such as:

var reg = new RegExp ("abc", "G");
var str = "3ABC4,5ABC6";
Alert (reg.exec (str));
Alert (Str.match (reg));

is ABC and ABC,ABC; Because match executes a global match query, and exec does not have a subexpression that only finds a match that returns.

5, when the expression contains sub-expressions in the case:

var reg = new RegExp ("A (BC)");
var str = "3ABC4,5ABC6";
Alert (reg.exec (str));
Alert (Str.match (reg));

You will find that the results of both executions are: ABC,BC;

6. When a regular expression object is defined as a global match

var reg = new RegExp ("A (BC)", "G");
var str = "3ABC4,5ABC6";
Alert (reg.exec (str));
Alert (Str.match (reg));

The result of both returns is ABC,BC and ABC,ABC,

Summarized as:

1, when the regular expression has no sub-expression, and is defined as a non-global match, the result of exec and match execution is the same, all return the first matching string content;

2, when the regular expression has no sub-expression, and defined as a global match, exec and match execution, do exist multiple matches, then match returns a plurality of element array;

3. When a regular expression has a child representation and is defined as a non-global match, the result of exec and match execution is the same as the 5th case above;

4, when the regular expression has a child representation, and is defined as a global match, exec and match execution results are different, at this time match will ignore the sub-expression, only find the full match regular expression and return all content, such as the 6th case;

It also says that exec has no relationship with global definition, while match is globally associated, and when defined as non-global, the results are the same

Description of the difference between the JavaScript regular expression exec () and match ()