JSFiddle - React, Tailwind, and code Playground

by ronilan

JavaScript

// [1,2,3,4,5].duplicate();
// [1,2,3,4,5,1,2,3,4,5]

Array.prototype.duplicate = function () {
    return this.concat(this);
}

console.log([1, 2, 3, 4, 5].duplicate());