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JavaScript RegExp ?= Quantifier

RegExp Object Reference JavaScript RegExp Object

Example

Do a global search for "is" followed by " all":

var str = "Is this all there is";
var patt1 = /is(?= all)/g;

The marked text below shows where the expression gets a match:

Is this all there is
Try it yourself »

Definition and Usage

The ?=n quantifier matches any string that is followed by a specific string n.

Tip: Use the ?!n quantifier to match any string that is NOT followed by a specific string n.


Browser Support

Internet Explorer Firefox Opera Google Chrome Safari

The ?= quantifier is supported in all major browsers.


Syntax

new RegExp("regexp(?=n)")

or

/regexp(?=n)/

Syntax with modifiers

new RegExp("regexp(?=n)","g")

or simply:

/\regexp(?=n)/g

RegExp Object Reference JavaScript RegExp Object