Here you can find the source of contains(txt)
String.prototype.contains = function(txt) { return (this.indexOf(txt) >= 0); }
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; };
String.prototype.contains = function (text) { return this.toLowerCase().indexOf(text.toLowerCase()) !== -1; };
String.prototype.contains = function(token, ignoreCase) { var _reg = 0, str = this.toString(), i; if(str && typeof token === "string") { if(ignoreCase === true) { token = token.toLowerCase(); str = str.toLowerCase(); while((i = str.indexOf(token)) !== -1) { str = str.substring(i + token.length); ...
String.prototype.contains = function (value) { "use strict"; var containsValue = false; if (this.indexOf(value) >= 0) { containsValue = true; return containsValue; };
String.prototype.containsAll = function(strings, index) { if(!Array.isArray(strings)) throw Error('1 argument is not an array'); return strings.every(string => this.includes(string, index), this);
String.prototype.contains = function contains(substring) { return this.indexOf(substring) !== -1; };
String.prototype.contains = function contains(value){ return this.indexOf(value) !== -1; };