JavaScript RegExp ?= Quantifier

A search for "is" followed by " all":

let text = "Is this all there is";
let pattern = /is(?= all)/g;

Description

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.

/(?=n)/ is an ECMAScript1 (ES1) feature.

ES1 (JavaScript 1997) is fully supported in all browsers:


Chrome	Edge	Firefox	Safari	Opera	IE
Yes	Yes	Yes	Yes	Yes	Yes

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

or

/regexp(?=n)/

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

or simply:

/regexp(?=n)/g