Here you can find the source of startsWith(str)
String.prototype.startsWith = function(str) { return ( str === this.substr( 0, str.length ) ); }
String.prototype.startsWith = function(start) { return this.indexOf(start) == 0; };
String.prototype.startsWith = function(start) { if(start == '') return true; else if(start == null || start.length > this.length) return false; else return this.substring(0,start.length) == start;
String.prototype.startsWith = function(str) { if (this.indexOf(str) === 0) { return true; }else { return false; };
String.prototype.startsWith = function(str) {return (this.match("^"+str)!==str)}
String.prototype.startsWith = function(str){ return this.substr(0, str.length) === str; };
String.prototype.startsWith = String.prototype.startsWith || function(str) { return this.indexOf(str) === 0; }; export default String;
String.prototype.startsWith = function(str) { return (this.indexOf(str) == 0); };
String.prototype.startsWith = function (str){ return this.indexOf(str) == 0; };
String.prototype.startsWith = function(str) { return (this.match("^"+str)==str); String.prototype.endsWith = function(str) { return (this.match(str+"$")==str);