text: function each(obj, callback) {
    var i = 0;
    var length = obj.length
    for (; i < length; i++) {
        value = callback(i, obj[i]);
    }
  }
  
  function eachWithCall(obj, callback) {
    var i = 0;
    var length = obj.length
    for (; i < length; i++) {
        value = callback.call(obj[i], i, obj[i]);
    }
  }
  
  var arr = Array.from({length: 1000000}, (v, i) => i);
  
  console.time('each')
  var i = 0;
  each(arr, function(index, item){
    i += item;
  })
  console.timeEnd('each')
  
  
  console.time('eachWithCall')
  var j = 0;
  eachWithCall(arr, function(index, item){
    j += item;
  })
  console.timeEnd('eachWithCall')