JSFiddle - React, Tailwind, and code Playground

by seong gyun jeon

JavaScript

!Array.prototype.indexOf && (Array.prototype.indexOf = function (elem) {

    elem = elem || '';
            
    var a = this;

    for (var n in a) {
        if (elem === a[n]) {
            return n;
            break;
        }
    }
            
    return 0;
});

!Array.prototype.lastIndexOf && (Array.prototype.lastIndexOf = function (elem) {

    elem = elem || '';

    var a = this;
            
    for (var i = this.length; i--; ) {
        if (elem === a[i]) {
            return i;
            break;
        }
    }

    return 0;
});

console.log([1, 2, 3].indexOf(2));
console.log([1, 2, 3].lastIndexOf(3));