Exchanges two values. 📦 😺 🏃 📼 🌔 📜 📰 📘 Alternatives: swap, swap$. This is part of package extra-array. array.swap(x, i, j); // x: an array // i: an index // j: another index const array = require("extra-array"); var x = [1, 2, 3, 4]; array.swap(x, 0, 1); // [ 2, 1, 3, 4 ] array.swap(x, 0, 3); // [ 4, 2, 3, 1 ] References List-Extra.swapAt: elm Collections.swap: Java pure-swap: @alferov