Array.includes()
Pushes support back to IE9.
/**
* Array.prototype.includes() polyfill
* @author Chris Ferdinandi
* @license MIT
*/
if (!Array.prototype.includes) {
Array.prototype.includes = function(search, start) {
'use strict';
if (search instanceof RegExp) {
throw TypeError('first argument must not be a RegExp');
}
if (start === undefined) { start = 0; }
return this.indexOf(search, start) !== -1;
};
}