form-cheatsheet/src/polyfills/String.prototype.includes.js

String.prototype.includes = function(search, start) {
  'use strict';
  if (typeof start !== 'number') {
	start = 0;
  }

  if (start + search.length > this.length) {
	return false;
  } else {
	return this.indexOf(search, start) !== -1;
  }
};