Info

Just testing the performace differences between iterating over an array and iterating over an object.

Preparation code

<script>
  var a1 = [],
      a2 = [],
      a3 = [],
      a4 = [],
      ob = {},
      collision = [];
  
  for (var i = 0; i < 5000; i++) {
   a1.push(i);
  }
  for (var i = 4000; i < 9000; i++) {
   a2.push(i);
  }
  for (var i = 0; i < 500000; i++) {
   a3.push(i);
  }
  for (var i = 400000; i < 900000; i++) {
   a4.push(i);
  }
  for (var i = 0; i < 5000; i++) {
   ob[i] = i;
  }
</script>

Test runner

Warning! For accurate results, please disable Firebug before running the tests. (Why?)

Java applet disabled.

for (var i = 0; i < a1.length; i++) {
 a1[i] = i;
}

for (var i in ob) {
 ob[i] = i;
}

// Yeah, i know you aren't supposed to do this
for (var i in a1) {
 a1[i] = i;
}

for (var i = 0; i < a1.length; i++) {
 for (var o = 0; i < a2.length; i++) {
  if (a2[o] == a1[i]) collision.push(a1[i]);
 }
}

var test = {};
for (var o in a1) {
 if (typeof a1[0] != 'Object') test[a1[o]] = a1[o];
 else test[a1[o]] = a1[o].join("_");
}
for (var o in a2) {
 if (test[a2[o]] !== undefined || (typeof a2[o] == 'Object' && test[a2[o].join("_")] !== undefined)) collision.push(a2[o]);
}

for (var i = 0; i < a3.length; i++) {
 for (var o = 0; i < a4.length; i++) {
  if (a4[o] == a3[i]) collision.push(a3[i]);
 }
}

var test = {};
for (var o in a3) {
 test[a3[o]] = a3[o];
}
for (var o in a4) {
 if (test[a4[o]] !== undefined) collision.push(a4[o]);
}

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Revisions

You can edit these tests or add even more tests to this page by appending /edit to the URL. Here’s a list of current revisions for this page:

• Revision 1: published on 15th February 2011
• Revision 2: published on 6th August 2011
• Revision 3: published by Tim on 17th February 2013

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