Iterating JavaScript object properties and arrays with for..in when ordering is important

Question

This has been an age old question and I am aware of the usual reasons for not using for..in or perhaps even objects when any sort of ordering is needed, but I r

Answer 1

There are more browsers than just those mentioned here: there are other current browsers and future browsers. None of them are obliged to implement any ordering when iterating over the properties of an object, and will not be for a long time, since the recent ECMAScript 5 specifies no ordering. Indeed, the Chrome development team is refusing to change its implementation despite vocal requests to make it conform with other browsers.

Any assumptions based on observed behaviour of a handful of current browsers is shaky at best; as observed, not all current browsers behave the same and future browsers may choose not to conform to your assumptions and have every right to do so. Therefore I strongly recommend not relying on any particular ordering in any of your code.