A polyfill for the String.prototype.matchAll method. Only available in Node12+ and most browsers.

readme.md

I know almost all browsers and Node installations support it, but Node 11 doesn't, and I kinda need that right now. So enjoy!

// Useable just like the normal matchAll:

let data = "Hello World!";
let rx = /[A-Z]/g;
let matches = [...data.matchAll(rx)];

console.table(matches);
/* Expected output:
┌─────────┬─────┬───────┬────────────────┬───────────┐
│ (index) │  0  │ index │     input      │  groups   │
├─────────┼─────┼───────┼────────────────┼───────────┤
│    0    │ 'H' │   0   │ 'Hello World!' │ undefined │
│    1    │ 'W' │   6   │ 'Hello World!' │ undefined │
└─────────┴─────┴───────┴────────────────┴───────────┘
*/

matchAll polyfill.js

if(!String.prototype.matchAll) {
    String.prototype.matchAll = function (rx) {
        if (typeof rx === "string") rx = new RegExp(rx, "g"); // coerce a string to be a global regex
        rx = new RegExp(rx); // Clone the regex so we don't update the last index on the regex they pass us
        let cap = []; // the single capture
        let all = []; // all the captures (return this)
        while ((cap = rx.exec(this)) !== null) all.push(cap); // execute and add
        return all; // profit!
    };
}

I think there's an edge case this doesn't handle:

matchAll() is not allowed to get "stuck" returning an empty string match infinitely, so we must make sure lastIndex always increases.

See https://github.com/google/closure-compiler/blob/master/src/com/google/javascript/jscomp/js/es6/string/matchall.js for a more complete polyfill. It doesn't handle unicode, but you can fix that by changing one the advancement based on whether the regex has unicode flag or not (see the link in the comment).

More generally, Closure library is usually a great source for simple yet battle-tested polyfills. (Definitely much better than the