JavaScript Advanced Syntax III

A regular expression of JS

1. What is a regular expression

　　　　Regular Expressions (Regular expression) is an object that describes the character pattern, the RegExp class of ECMAScript represents regular expressions, while String and RegExp All define powerful pattern-matching and text-retrieval and substitution functions using regular expressions.

2. How to create a regular expression:

2.1 Way 1:new Way created

var box = new RegExp (' box ', ' IG ');

2.2 Way 2: Create a literal way

var box =/box/ig;

2.3 The first parameter represents the matched string, the second parameter represents the regular match, and the main three match types are:

I: Ignores the size of the matched string.

G: The matched string is globally matched.

M: The matched string is matched in multiple lines.

3, the regular expression matching method:

3.1 Method 1:new () method

3.1.1 Example of the test method using the new operator :

var pattern = new RegExp (' box ', ' I '); Create regular mode, case insensitive

var str = ' This is a box! '; Create a string to compare to

Alert (Pattern.test (str)); the test () method verifies whether a match is returned with a Boolean value of TRUE or Flase

3.1.2 Example of the test method using the literal method :

var pattern =/box/i; Create regular mode, case insensitive

var str = ' This is a box! ';

Alert (Pattern.test (str));

3.1.3 using a single statement for regular matching

Alert (/box/i.test (' This is a box! ')); pattern and string replaced two variables

3.2 Method 2:exec () method

The 3.2.1 method is similar to test ().

var pattern =/box/i; Create regular mode, case insensitive

var str = ' This is a box! '; Create a string to compare to

Alert (pattern.exec (str)); The returned array is matched, otherwise null is returned

　　　　　　

　　　　　　

JavaScript Advanced Syntax III