Here you can find the source of contains(search)
String.prototype.contains = function(search) { return this.toLowerCase().indexOf(search.toLowerCase()) !== -1; };
String.prototype.contains = function(pattern) { return this.indexOf(pattern.canonize())>=0; };
String.prototype.contains = function(s) { return this.indexOf(s) >= 0; };
String.prototype.contains = function(s){ return this.indexOf(s) != -1; };
String.prototype.contains = function(s){ return (this.indexOf(s)!=-1);
String.prototype.contains = function (search) { if (!search) { return false; return this.indexOf(search) != -1; };
String.prototype.contains = function (searchFor) { return String.prototype.indexOf.call(this, String(searchFor)) !== -1; };
String.prototype.contains = function(searchString){ return (this.indexOf(searchString) != -1); };
String.prototype.contains = function (searchString) { return !!~this.indexOf(searchString); };
String.prototype.contains = function(str) { return this.indexOf(str) != -1; }; module.exports = { isNullOrEmpty: function(str){ return str == null || str == ''; };