Performance of Array vs. Object

JavaScript performance comparison

Test case created by Christopher Froehlich

Info

After seeing http://jsperf.com/javascript-associative-vs-non-associative-arrays, I thought the test could be improved.

Preparation code

 
<script>
Benchmark.prototype.setup = function() {
    var arr = [],
        i,
        obj = {};
    for(i = 0; i < 10000; i += 1) {
        arr.push(i);
        obj[i] = i;
    }
   
    function getRandomIndex(obj) {
       var idx = Math.floor(Math.random()*9999);
       if(false === obj.hasOwnProperty(idx)) {
          while (false === obj.hasOwnProperty(idx)) {
              idx = Math.floor(Math.random()*9999);
          }
       }
       return idx;
    }
};
</script>

Test runner

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Testing in unknown unknown
Test Ops/sec
Array Performance
var idx = getRandomIndex(arr),
    a = arr[idx];

arr[idx] = Math.floor(Math.random()*9999);
arr.splice(idx,0);
arr[length] = a;
 
pending…
Object Performance
var idx = getRandomIndex(obj),
    a = obj[idx];

obj[idx] = Math.floor(Math.random()*9999);
delete obj[idx];
obj[idx] = a;
pending…

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