$.each() fails on an object when the object has a key named 'length'

[[email protected]…]

If you have an object, like this:

var obj = { name: "something", length: 12, height: 32 };

and then you try to iterate over it using $.each:

$.each( obj, function( key, value ) {
    ...
} );

The inner function is never called because jquery treats the object as an array instead of an object. This behavior is unexpected; it should either be documented or fixed.

[jitter]

This exact behavior is well documented thus $.each behaves exactly as expected.

From ​http://api.jquery.com/jQuery.each/

Arrays and array-like objects with a length property (such as a function's arguments object) are iterated by numeric index, from 0 to length-1. Other objects are iterated via their named properties.

Here a ​live test case to show what is happening.

[anonymous]

I fail to see how a json object with a quoted length property could be considered an array-like object.

[anonymous]

This is also a problem in jQuery templates when using {{each}} to iterate through an object which happens to have a "length" key.

[jboesch]

I think we can fix this issue. If jQuery.map is supporting objects in 1.6 (and works with length props) I think we should maybe consider adding it here.

Here is what the code is right now being used in jQuery.each (object/array detection):

isObj = length === undefined || jQuery.isFunction( object );

This can be changed to what's being used in jQuery.map (v 1.6):

isArray = elems instanceof jQuery || length !== undefined && typeof length === "number" && ( ( length > 0 && elems[ 0 ] && elems[ length -1 ] ) || jQuery.isArray( elems ) ) ;

Here's Dan's isArray var in action in the jQuery.map function: ​https://github.com/jquery/jquery/pull/299/files

Here's a fiddle with me changing that one line: ​http://jsfiddle.net/jboesch26/Ungsa/

This would allow looping over objects with length props. This newEach2 proposal seems to be slightly faster as well: ​http://jsperf.com/each-object-supporting-length-key/6

If this is cool, I'll make a pull request.

[jboesch]

Pull request: ​https://github.com/jquery/jquery/pull/336/files

[sindresorhus]

#11573 is a duplicate of this ticket.

[dmethvin]

#11810 is a duplicate of this ticket.

[dmethvin]

#12130 is a duplicate of this ticket.