jquery - code review

This seems poorly symmetrical. The code to take a string and turn into zero or more selected options in a select list is one line. The code to do the inverse is a story. Am I missing some pattern for doing the later? I originally had it as one line without the null check and got a JavaScript null reference.

What about that ?

Christophe Verré wrote:What about that ?
var selectedValues = $('#b').val() || []; $('#a').val(selectedValues.join(','));

.val() returns a string so the join is useless.

$(...) is expensive, you want to try to minimize the amount of times you look things up.

Eric Pascarello wrote:.val() returns a string so the join is useless.

http://api.jquery.com/val/

In the case of <select multiple="multiple"> elements, the .val() method returns an array containing each selected option.

I'd use chaining and the this pointer in the handler body to minimize calls to $().

// the one liner gives an error
// $('#a').val($('#b').val().join(',');

That line is missing a )

Running example here: http://jsbin.com/ivubi4/

Christophe Verré wrote:

Eric Pascarello wrote:.val() returns a string so the join is useless.

http://api.jquery.com/val/

In the case of <select multiple="multiple"> elements, the .val() method returns an array containing each selected option.

Totally missed select in her question...

I learned two things in this thread. The idiom of merging things with or (which is very Perl like but it didn't occur to me for JavaScript) and that you can chain an event handler with something that executes now. Both of which make perfect sense now that they came up.