JavaScript RegExp ?! Quantifier

Last Updated : 10 Dec, 2024

The RegExp ?!m Quantifier in JavaScript is used to find the match of any string which is not followed by a specific string m.

JavaScript

// 3-digits not followed by any numbers
const str = "123Geeks12345@";
const regex = /\d{3}(?!\d)/g;

const match = str.match(regex);
console.log(match);

Output

[ '123', '345' ]

Syntax

/?!m/

Example 1: Matching the words ‘Geeks’ not followed by 123 in the whole string.

JavaScript

let str = "Geeks for 123 Geeks@";
let regex = /Geeks(?!123)/g;
let match = str.match(regex);

console.log("Found " + match.length
    + " matches: " + match);

Output

Found 2 matches: Geeks,Geeks

Example 2: Replacing the word ‘128’ with ‘#’ symbol.

JavaScript

let str = "@128Geek128";
let regex = new RegExp("128(?!ee)", "gi");
let replace = "#";
let match = str.replace(regex, replace);
console.log("New string: " + match);

Output

New string: @#Geek#

JavaScript RegExp ?! Quantifier

Syntax

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