Check duplicated items in array, with JavaScript

checkduplicationinarray.js

//
// Array related functions
//

function eliminateDuplicates(arr) {
  var i,
      len=arr.length,
      out=[],
      obj={};

  for (i=0;i<len;i++) {
    obj[arr[i]]=0;
  }
  for (i in obj) {
    out.push(i);
  }
  return out;
}

function hasDuplicates(arr) {
    return (new Set(arr)).size !== arr.length;
}

function hasDuplicatesInStringArray(strarray) {
    var valuesSoFar = Object.create(null);
    for (var i = 0; i < strarray.length; ++i) {
        var value = strarray[i];
        if (value in valuesSoFar) {
            return true;
        }
        valuesSoFar[value] = true;
    }
    return false;
}