What does lookahead assertion mean in javascript

Explanation

1. The first assertion is to tell JavaScript to search forward in the string for a matching pattern. Might be useful if you want to search for multiple matching patterns on the same string.

2. There are two types of lookahead assertions: positive lookahead assertions and negative lookahead assertions.

Example

let quit = "qu";
let noquit = "qt";
let quRegex= /q(?=u)/;
let qRegex = /q(?!u)/;
quit.match(quRegex);
noquit.match(qRegex);

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