A better jQuery.map

[flesler]

Hi, today I realized jQuery.map doesn't support hashes(associative arrays). I'm surprised, this is a behavior I'd assume it'd be included.

I added the changes to make this possible. In addition, added a third, optional, argument that is the return object. So it's possible to map on a existing object.

I made it so flexible, that one can map from an array to a hash, and the other way around as well. This is mostly useful to collect the keys or values from a hash, or to map an array of elements to an object(like setArray). It will handle array-like objects, and will treat them as arrays

I optimized the array concatenation, so now it's only done once, in the end, and now, there's no need for array-wrapping the returned data.

I think the length of the code remains more or less the same, so this should be doable.

I tested all the cases in IE6, FF2, Safari 3, and Opera 9.

I hope this helps

[flesler]

Proposal

[flesler]

Tried all these cases in IE6, FF2, Opera 9.25 and Safari 3 and they all worked well.

var keys = $.map( {a:1,b:2}, function( v, k ){
	return k;
}, [ ] );
alert(keys);

var values = $.map( {a:1,b:2}, function( v, k ){
	return v;
}, [ ] );
alert(values);

var mapped = $.map( document.getElementsByTagName('script'), function( v, k ){
	return v;
}, {length:0} );
alert(mapped);

var flat = $.map( Array(8), function( v, k ){
	return k % 2 ? k : [k,k,k];//try mixing array and regular returns
});
alert(flat);

[joern]

Could you convert that to the testsuite, too?

[flesler]

The tests for the test suite

[joern]

Commited test in [5342].

[joern]

Your patch must be tested against the benchmark before applying it, as map is a core function of jQuery. Its raw speed has higher priority then being useful for other cases. If we can do both, even better.

[flesler]

Shouldn't you/we accept the change before adding the tests to the test suite ? Or it will fail for others that haven't applied the proposed diff.

[flesler]

I meant you/we add the test, not accept. I didn't mean to say it's on me to accept :)

[flesler]

Updated to match against [5753]

[SlexAxton]

Is this still something you guys think should make it into core? It's been a little while...

[trac-o-bot]

Automatically closed due to 14 days of inactivity.

[jordan@…]

I think the performance his is too much as per joern's comment: ​http://jsfiddle.net/jboesch26/mmhwZ/4/

[jordan@…]

I've made some changes to make sure this doesn't affect performance that much: ​https://github.com/jquery/jquery/pull/238

[Rick Waldron]

#8328 is a duplicate of this ticket.

[Rick Waldron]

I've spent some time with the newest patch and perf comparing it to the existing, I'm indifferent about the perf. My issue is this...

// Provided test...

var keys = jQuery.map( {a:1,b:2}, function( v, k ){
	return k;
});

equals( keys.join(""), "ab", "Map the keys from a hash to an array" );


// But this is totally bonkers:
var keys = jQuery.map( {a:1,b:2, length: 2 }, function( v, k ){
	return k;
});

equals( keys.join(""), "ab", "Map the keys from a hash to an array, has a length property" );

// > "01" 
// expected: "ab"

[Rick Waldron]

Reopening this for the current review

[jboesch]

Updated pull request can be found here: ​https://github.com/jquery/jquery/pull/252

[Rick Waldron]

Did you look at the weird test results I posted previously?

[trac-o-bot]

Because we get so many tickets, we often need to return them to the initial reporter for more information. If that person does not reply within 14 days, the ticket will automatically be closed, and that has happened in this case. If you still are interested in pursuing this issue, feel free to add a comment with the requested information and we will be happy to reopen the ticket if it is still valid. Thanks!

[john]

Landed.

[yk]

Why map to the object creates an array? I do not quite understand the history of this ticket, but the original patch was different behavior (map object to object) and I think it's more logical.

[danheberden]

For an end use standpoint, you're right - but internally, worrying about something else being returned from map besides an array is out of scope for the patch. Even then, the patch isn't designed to be full featured by any means - just a simple way to parse out keys or values into an array.

That's not to say someone can't make a plugin to offer the object to object map - not sure how that'd look recursively though..