Here you can find the source of contains(substring)
String.prototype.contains = function(substring) { return !!this.match(new RegExp(substring, 'i')); }
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; };
String.prototype.contains = function(substr) return this.indexOf(substr) > -1;
String.prototype.contains = function(substring) { return this.indexOf(substring) != -1;
String.prototype.contains = function(substring, ignoreCase) { var lowerSubString = substring.toLowerCase(), lowerThis = this.toLowerCase(); if (ignoreCase) { return lowerThis.indexOf(lowerSubString) > -1; } else { return this.indexOf(substring) > -1;
String.prototype.contains = function (t) { return this.indexOf(t) != -1; };
String.prototype.contains = function(term){ return this.indexOf(term) > -1; };