array-findindex-polyfill/index.js

Simple ES6 Array.prototype.findIndex polyfill for older environments.

/**
 * Array.prototype.findIndex
 *
 * @ref https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/findIndex
 */

module.exports = (function() {
    if (!Array.prototype.findIndex) {
        Array.prototype.findIndex = function(predicate) {
            if (this === null) {
                throw new TypeError('Array.prototype.findIndex called on null or undefined');
            }

            if (typeof predicate !== 'function') {
                throw new TypeError('predicate must be a function');
            }

            var list = Object(this);
            var length = list.length >>> 0;
            var thisArg = arguments[1];
            var value;

            for (var i = 0; i < length; i++) {
                value = list[i];
                if (predicate.call(thisArg, value, i, list)) {
                    return i;
                }
            }

            return -1;
        };
    }
})();