Global Variables vs Local Variables vs Properties (v40)

Revision 40 of this benchmark created on

Description

This test compares the performance of global variables to local variables within functions.

Global variables should be slower because they do not exist in a function's activation object. JavaScript must traverse the Scope Chain to locate global variables.

Preparation HTML

<script>
  var a,b=0;
  function x() {
    for(a=0;a<64;a++)
      b+=a;
  }

  function w() {
    for(window.a=0;window.a<64;window.a++)
      window.b+=window.a;
  }

  function wt() {
    for(this.a=0;this.a<64;this.a++)
      this.b+=this.a;
  }

  function y() {
    var c,d=0;
    for(c=0;c<64;c++)
      d+=c;
  }

  function z(){
    var c = a,
        d = b;

    for(c=0;c<64;c++)
       d+=c;
  }

  function q(a,b){
    for(a=0;a<64;a++)
       b+=a;
  }

  function k(c,d){
    for(c=0;c<64;c++)
       d+=c;
  }

  var obj = {
    a: 0,
    b: 0,
    p: function() {
      for(this.a=0;this.a<64;this.a++)
        this.b+=this.a;
    }
  }
</script>

Setup

a = 0;
    b = 0;

Test runner

Ready to run.

Testing in
TestOps/sec
Global variables
x();
ready
Local variables
y();
ready
Cached global variables
z();
ready
Window
w();
ready
Window (this)
wt();
ready
Params
q();
ready
Cached params
k(a,b);
ready
Object Properties
obj.p(); // extra operation (obj lookup). not valid test unfortunately.
ready

Revisions

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