RegExp Reference Properties

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  • turned_in_notReference Properties
    • RegExp.$1-$9
    • RegExp.input ($_)
    • RegExp.lastParen ($+)
    • RegExp.lastMatch ($&)
    • RegExp.leftContext ($`)
    • RegExp.rightContext ($')
  • To run below examples, try it inside <script> tag, in a basic html file


RegExp.$1-$9

To get Nth group substring match

Syntax - Use anyone

RegExp.$N     // where N ranges from 1-9
RegExp["$N"] // where N ranges from 1-9

For example : 

var str="bookWorld";
var pattern=/(oo)(..)/ig;
pattern.exec(str);
alert(RegExp["$1"]);
// Output: oo

Comment : Return the 1st group (oo) match ('oo' in above case)



RegExp.input ($_)

To get the string against which a current regular expression is matched

Syntax - Use anyone

RegExp.input   //Full-format
RegExp.$_     //Short-format
RegExp["$_"]  //Short-format

For example : 

var str="bookWorld";
var pattern=/(oo)(..)/ig;
pattern.test(str);
alert(RegExp.$_);
// Output: bookWorld

Comment : Return used input text ('bookWorld' in above case)



RegExp.lastParen ($+)

To get the last group substring match

Syntax - Use anyone

RegExp.lastParen
RegExp.$+
RegExp['+'] // use this since, "+" has a special meaning in javaScript

For example : 

var str="bookWorld";
var pattern=/(oo)(..)/ig;
pattern.exec(str);
alert(RegExp["$+"]);
// Output: kW

Comment : Return the last group (..) match ('kW' in above case)



RegExp.lastMatch ($&)

To get the last matched substring

Syntax - Use anyone

RegExp.lastMatch
RegExp.$&
RegExp['$&'] // use this since, "&" has a special meaning in javaScript

For example : 

var str="WorkBook";
var pattern=/kB/ig;
pattern.test(str);
alert(RegExp["$&"]);
// Output: kB

Comment : Returns last matched substring ('kB' in above case)



RegExp.leftContext ($`)

To get the substring preceding the most recent match

Syntax - Use anyone

RegExp.leftContext
RegExp.$`
// use this since, "`" has a special meaning in javaScript
RegExp['$`']

For example : 

var str="WorkBook";
var pattern=/kB/ig;
pattern.test(str);
alert(RegExp["$`"]);
// Output: Wor

Comment : Returns left-side of last matched substring ('Wor' in above case)



RegExp.rightContext ($')

To get the substring following the most recent match

Syntax - Use anyone

RegExp.rightContext
RegExp.$'
RegExp["$'"]  // use this since, "'" has a special meaning in javaScript

For example : 

var str="WorkBook";
var pattern=/kB/ig;
pattern.test(str);
alert(RegExp["$'"]);
// Output: ook

Comment : Returns right-side of last matched substring ('ook' in above case)



* Important - Useful sometimes

You can try reference properties except "RegExp.input ($_)" with javaScript string replace( ) function

  • Here, you can directly use symbols of the specific reference properties
var str="bookWorld goodWorld";
var pattern=/(oo)(..)/ig;
alert(str.replace(pattern,"@-$&-@"));
// Output: b@-ookW-@orld g@-oodW-@orld

Comment : It will replace all matches made with pattern to "@-$&-@"
Where "$&" will hold,
for the 1st matched substring (which in above case $& = "ookW") and
for the 2nd matched substring (which in above case $& = "oodW")
So, finally
1st match replaced with "@-ookW-@" and
2nd match replaced with "@-oodW-@"



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