Here you can find the source of contains(string, index)
// String.prototype.contains String.prototype.contains = function (string, index) { return this.indexOf(string, index) !== -1; };
String.prototype.contains = function(str, index) { return (this.indexOf(str, index) !== -1) ? true : false;
String.prototype.contains = function(str,startIndex) { return -1 !== String.prototype.indexOf.call(this,str,startIndex); };
String.prototype.contains = function(strPattern){ if(typeof strPattern !== 'string') return false; var pattern = new RegExp(strPattern, "i"); return pattern.test(this); console.log("teste".contains("teste"));
String.prototype.contains = function(string) { return (this.indexOf(string) != -1);
String.prototype.contains = function(string) { return this.indexOf(string) > -1; };
String.prototype.contains = function (string, index) { return this.indexOf(string, index) !== -1; };
String.prototype.contains = function(stringSet) { for (var i=0;i<stringSet.length;i++) { if (this.indexOf(stringSet[i]) >= 0) return true; return false; };
String.prototype.contains = function(strings, index) { if(!Array.isArray(strings)) throw Error('1 argument is not an array'); return strings.some(string => this.includes(string, index), this);
String.prototype.contains = function (subString) { return this.indexOf(subString) !== -1; };