Isogram created by jarellano01 - https://repl.it/ETwe/1

Isogram.js

function isIsogram(str){
  var strLower = str.toLowerCase()
  var strArray = strLower.split("");
  
  var duplicateCheck = [];
  for(var i = 0; i < strArray.length; i++){
  	if (duplicateCheck.indexOf(strArray[i]) == -1){
  		duplicateCheck.push(strArray[i]);
  	}
  	else return false 
  	
  	if(strArray[i] == strArray[i+1]){
  		return false
  	}
  }
  
  return true;
  
}

An isogram is a word that has no repeating letters, consecutive or non-consecutive.