3 ms·

For-loops like "for (i=0;i<myLinkCollection.length;i++)" should always be written like "for (var i=..."), unless there's an explicit "var i;" declaration somewh

by ramen 17y ago

For-loops like "for (i=0;i<myLinkCollection.length;i++)" should always be written like "for (var i=..."), unless there's an explicit "var i;" declaration somewhere. Otherwise, this creates a global variable "i", which can lead to some very confusing bugs if another function is called that also references the global "i".

ams6110 17y ago
But don't make the mistake of assuming that when writing "for (var i=...)" that i is scoped to the loop block. JavaScript does not have block scope. It only has function scope, with the "Global Object" scope being the top level scope.
- maxwell 17y ago
  Only with JS <1.7. Otherwise you get block scope by using 'let instead of 'var.
  - tumult 17y ago
    Only SpiderMonkey (Gecko) has that. And it will remain that way for the foreseeable future.
maxwell 17y ago
You'll get better performance with for (var i=0, l=myLinkCollection.length; i<l; i++) { } http://robertnyman.com/2008/04/11/javascript-loop-performance/ http://robertnyman.com/2008/04/11/javascript-loop-performanc...
- WalkingDead 17y ago
  Probably first time I am seeing a micro-optimization having some really significant impact on a micro-benchmark test.