JavaScript RegExp Objects

The RegExp object is an object in native JavaScript that represents a regular expression.

The object is created in the following way: var RegExp = new RegExp (pattern, attributes);

Parameter pattern specifies the regular expression rule or a string representing the regular expression pattern;
The parameter attributes is an optional parameter that represents the modifier for the matching Pattern. Consists of 3 parameters:

1. I: Perform an insensitive match to the case;

<script text= "text/javascript" > var txt = ' Hello world! ' var New RegExp (' Hello ', ' i '); if　　(reg.test (txt)) {console.log(txt.match (reg)); }</script>

2. G: Perform a global match (to find all occurrences rather than to find the first match and stop);

 <script text= "text/javascript" > var  txt = ' This is just a test. ' var  reg = new  RegExp (' is ', ' G '); //  var  reg01 = new  RegExp (' is ', ' GI '); //     case-insensitive  if   // ["is", "is"]  console.log (txt.match (reg). length); // 2  }  </script> 

3. M: Performs multi-line matching (if This property is not set, ^ ($) only matches the start (end) position of the entire searched string; if this property is set, ^ ($) can also match the position of the searched string after "\ r" or "\ n").

<script type= "text/javascript" >//the following code is not able to match the string "an", although "an" is followed by a newline, but "an" is not the end of the string line.     varTxt1 = ' This is an\n Apple '; varREG1 =/an$/; Console.log (txt1.match (reg1));//NULL        //the following code can be matched to the string "an"    varTxt2 = ' This is an\n Apple '; varREG2 =/an$/m; Console.log (txt2.match (reg2));//["an", index:8, input: "are you an?" Apple "]        //the Following is a multi-line match beginning example    varTXT3 = ' This is an\n Apple '; varReg3 =/^\sapp/; Console.log (txt3.match (reg3));//NULL        varTXT4 = ' This is an\n Apple '; varREG4 =/^\sapp/m;///^ app/mConsole.log (txt4.match (reg4));//["app", index:11, input: "this was an?" Apple "]</script>

I,g,m three modifiers can be combined and used in combination with one another.

In the example above in the M modifier, var reg4 =/^\sapp/"\" is an escape character, and "\" in the regular expression should be replaced with "\ \" if the constructor is used to create the RegExp object:

<script type= "text/javascript" >    var txt4 = ' This is an\n Apple ';     var New RegExp (' ^\\sapp ', ' m ');    Console.log (txt4.match (reg4)); // ["app", index:11, input: "this was an?" Apple "]</script>

RegExp Object Properties

1.global

Returns whether the regular expression has a "g" modifier;

<script type= "text/javascript" >    var txt = ' This is just a test ';     var New RegExp (' St ', ' G ');     if (reg.global) {        console.log (txt.match (reg)); // ["st", "st"]     }</script>

2.ignoreCase

Returns whether the regular expression has an "i" modifier;

3.multiline

Returns whether the regular expression has an "m" modifier;

4.lastIndex

Marks the position of the string where the next match starts;

<script type= "text/javascript" >    var txt = ' If you love code, You should code everyday. ' ;     var New RegExp (' ou ', ' g ');     var length = txt.match (reg). length;      for (var i = 0; i < length; i++) {        reg.test (txt);        Console.log (reg.lastindex);    } </script>

5.source

Returns a regular expression for pattern-matching text or expression that does not include the modifier "i", "g", "m" in the returned text, nor the delimiter used for the direct amount of the regular expression

<script>    varnew RegExp (' Yoho ', ' m ');     var New RegExp (' \\w ');     var reg3 =/\w/m;    Console.log (reg1.source); // Yoho    Console.log (reg2.source); // \w    Console.log (reg3.source); // \w</script>

RegExp Object Methods

1.compile

Change or recompile regular expressions (this method is not supported by opera Browser)

The following methods can be implemented for the redefinition of regular expressions, so I am not very clear about the application scenario for this method

<script>    varnew RegExp (' ou ', ' g ');     =/\w/; </script>

2.exec

Retrieving the matching results of a regular expression in a string

<script>    var txt = ' If you love code, should code everyday. ' ;     var New RegExp (' ou ', ' g ');     var length = txt.match (reg). length;      for (var i = 0; i < length; i++) {        console.log (reg.exec (txt));    } </script>

3.test

Detects if a string matches a matching regular expression

<script>    var txt = ' I code everyday. ' ;     var New REGEXP (' code ');    Console.log (reg.test (txt)); // true</script>

JavaScript RegExp Objects