in Object vs Array.indexOf

JavaScript performance comparison

Test case created

Info

Is it faster to look up the existence of a key on an object or the existence of an item in an array.

Preparation code

 
<script>
Benchmark.prototype.setup = function() {
    if (!Array.prototype.indexOf) {
        Array.prototype.indexOf = function (searchElement /*, fromIndex */ ) {
            "use strict";
            if (this == null) {
                throw new TypeError();
            }
            var t = Object(this);
            var len = t.length >>> 0;
            if (len === 0) {
                return -1;
            }
            var n = 0;
            if (arguments.length > 1) {
                n = Number(arguments[1]);
                if (n != n) { // shortcut for verifying if it's NaN
                    n = 0;
                } else if (n != 0 && n != Infinity && n != -Infinity) {
                    n = (n > 0 || -1) * Math.floor(Math.abs(n));
                }
            }
            if (n >= len) {
                return -1;
            }
            var k = n >= 0 ? n : Math.max(len - Math.abs(n), 0);
            for (; k < len; k++) {
                if (k in t && t[k] === searchElement) {
                    return k;
                }
            }
            return -1;
        }
    }
   
    var obj = {},
    arr = [];
   
    for(var i = 0; i < 1000; i++) {
      if(i % 2 === 0) {
        arr.push(obj[i] = true);
      }
    }
};
</script>

Test runner

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Testing in unknown unknown
Test Ops/sec
in
var count = 0;

for(var i = 0; i < 1000; i++) {
  if(i in obj) {
    count++;
  }
}
 
pending…
indexOf
var count = 0;

for(var i = 0; i < 1000; i++) {
  if(arr.indexOf(i) > -1) {
    count++;
  }
}
 
pending…
[] !== undefined
var count = 0;

for(var i = 0; i < 1000; i++) {
  if(obj[i] !== undefined) {
    count++;
  }
}
 
pending…
hasOwnProperty
var count = 0;

for(var i = 0; i < 1000; i++) {
  if(obj.hasOwnProperty(i)) {
    count++;
  }
}
 
pending…

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