Check for repeated characters in a string Javascript

function chkRepeat(word) {
    var wordLower = word.toLowerCase();
    var wordSet = new Set(wordLower);
    var lenWord = wordLower.length;
    var lenWordSet =wordSet.size;

    if (lenWord === lenWordSet) {
        return "false"
    } else {

This will do:

function isIsogram (str) {
    return !/(.).*\1/.test(str);

you can use .indexOf() and .lastIndexOf() to determine if an index is repeated. Meaning, if the first occurrence of the character is also the last occurrence, then you know it doesn't repeat. If not true, then it does repeat.

var example = 'hello';

var charRepeats = function(str) {
    for (var i=0; i<str.length; i++) {
      if ( str.indexOf(str[i]) !== str.lastIndexOf(str[i]) ) {
        return false; // repeats
  return true;

console.log( charRepeats(example) ); // 'false', because when it hits 'l', the indexOf and lastIndexOf are not the same.

(A recursive solution can be found at the end, of this answer.)

You could just use the builtin javascript Array functions some MDN some reference

 var text = "test".split("");
   return a.lastIndexOf(v)!=i;

callback parameters:
v ... current value of the iteration
i ... current index of the iteration
a ... array being iterated

.split("") create an array from a string
.some(function(v,i,a){ ... }) goes through an array until the function returns true, and ends than right away. (it doesn't loop through the whole array, which is good for performance)

Details to the some function here in the documentation

Tests, with several different strings:

var texts = ["test", "rest", "why", "puss"];

for(var idx in texts){
    var text = texts[idx].split("");
    document.write(text + " -> " + text.some(function(v,i,a){return a.lastIndexOf(v)!=i;}) +"<br/>");
  //tested on win7 in chrome 46+

If recursion is really needed.

Update for recursion:

//recursive function
function checkString(text,index){
    if((text.length - index)==0 ){ //stop condition
        return false; 
        return checkString(text,index + 1) 
        || text.substr(0, index).indexOf(text[index])!=-1;

// example Data to test
var texts = ["test", "rest", "why", "puss"];

for(var idx in texts){
    var txt = texts[idx];
    document.write( txt +  " ->" + checkString(txt,0) + "<br/>");
//tested on win7 in chrome 46+