Here you can find the source of endsWith(string)
// String.prototype.endsWith String.prototype.endsWith = function (string) { var index = arguments.length < 2 ? this.length : arguments[1]; return this.indexOf(string) === index - string.length; };
String.prototype.endsWith = function (str){ return this.indexOf(str) == this.length - str.length - 1; };
String.prototype.endsWith = function (str){ return this.slice(-str.length) == str; }; String.prototype.startsWith = function (str){ return this.slice(0, str.length) == str; };
String.prototype.endsWith = function (str) { return this.slice(this.length - str.length, this.length) === str; };
String.prototype.endsWith = function(str) { if (str == this.substring(this.length - str.length, this.length)) return true; return false;
String.prototype.endsWith = function (string) { var index = arguments.length < 2 ? this.length : arguments[1]; return this.indexOf(string) === index - string.length; };
String.prototype.endsWith = function (string) { var index = arguments.length < 2 ? this.length : arguments[1]; var foundIndex = this.indexOf(string); return foundIndex !== -1 && foundIndex === index - string.length; };
String.prototype.endsWith = function (string) { var index = arguments.length < 2 ? this.length : arguments[1]; var foundIndex = this.lastIndexOf(string); return foundIndex !== -1 && foundIndex === index - string.length; };
String.prototype.endsWith = function(substr) { return (this.match(substr + "$") == substr); };
String.prototype.endsWith = function (substring) { var stringCut = this.substring(this.length - substring.length); return stringCut === substring;