New in JavaScript: Array.findLast and Array.findLastIndex (#note)

An update of MDN's browser-compat-data caught my eye today. Finding values in Arrays is a common practice via find and findIndex. These methods iterate from the array beginning, though.

const things = [{v: 1}, {v: 2}, {v: 3}, {v: 4}, {v: 5}];

things.find(elem => elem.v > 3); // {v: 4}
things.findIndex(elem => elem.v > 3); // 3

If you wanted to search your array starting from the end, you had to reverse the array and use the provided methods. That's not great because it requires an unnecessary array mutation.

Luckily, there's an ECMAscript proposal for findLast and findLastIndex.

const things = [{v: 1}, {v: 2}, {v: 3}, {v: 4}, {v: 5}];

things.findLast(elem => elem.v > 3); // {v: 5}
things.findLastIndex(elem => elem.v > 3); // 4

The proposal is currently on Stage 3 and will be implemented in Chromiums and Safari soon. For the rest, core-js and Babel already provide a polyfill.

That's a sweet little language addition. Go JavaScript!