title: Why array is getting bigger after loop?
body: <p>I'm trying to change a color of background cells in google sheets so I wrote a code that I guess should do the job after putting into <code>.setBackgrounds()</code> (to mark duplicates)</p>
  <p>But I have no idea why after looping <code>calkiemNowa</code> array is getting few times bigger then the original arrays.</p>
  <p>Values length is around 4k and nowaArr has 200 elements, but the output <code>calkiemNowa</code> has something around 120k elements so I am getting error of too many values...</p>
  <p>The goal seems to be simple: check if in the <code>Values</code> are the same elements as in <code>nowaArr</code> and mark them red.</p>
  <p>Why <code>calkiemNowa</code> is getting that big? is it because of double loop?</p>
  <pre><code>    var nowaArr =[[1376064101], [1376064201], [1376613201], [1376613301], [1376613401], [1376613501], [1376613601], [1376613701], [1376613801], [1376613901], [1216987501], [1256524001], [1256639901], [1296132901], [1296133001], [1296133101], [1296133201]];
      var values = [[1326M76501], [1326M76301], [1326M76101], [1326M76901], [1326M76701], [1296133901], [1296133701], [1296133801], [1326H14201], [1216991801], [1236N12801], [1236F76701], [1326H16101], [1376616801], [1236F78101], [1236N13401], [1326G44401], [1236F79301], [1326848401], [1326N08801], [1326N08601], [1326N12601], [1326N09801], [1326N14701], [1326N15401], [1326N09601], [1326N09001], [1326N14001], [1326N11901],[1296133201]];
  
  function checkArrays(){
  
  var calkiemNowa = [];
  for(var i = 0; i &lt; values.length; i++){
    for(var j = 0; j &lt; nowaArr.length; j++){
      if(values[i][0] === nowaArr[j][0]){
        calkiemNowa.push('red');
      }else{
        calkiemNowa.push('null');
      }
    }
  }
  return calkiemNowa;
  }
  </code></pre>