Detect repeating letter in an string in Javascript

Question

code for detecting repeating letter in a string.

var str=\"paraven4sr\";
var hasDuplicates = (/([a-zA-Z])\\1+$/).test(str)        
alert(\"repeating string \         


        

Answer 1

To just test duplicate alphanumeric character (including underscore _):

console.log(/(\w)\1+/.test('aab'));