Sometimes you need to ask a users for multiple answers to a single question. But what's the best way to go about it?

A multiselect input field is kind of strange for the user, sticks out and doesn't really behave like everything else on the web.

A bunch of checkboxes is better for the user ... but have you ever tried handling a form with dynamically created checkboxes? Let alone creating useful tests and consolidating everything into a single list of values. No decent forms framework will let you do that easily.

I had to solve this similar problem for a time and attendance software I worked on, so I made a Javascript thing to convert a select field into a checkbox-field. Then I made it into a simple jquery plugin thing for everyone to use :)

Check out the demo!

The idea is pretty simple:

take a select, turn it into a list of options

every option becomes a Checkbox model in a collection

render each Checkbox as a CheckboxView

connect everything with some events

What I really love about the Backbone approach is that all of this works almost magically. Instead of bending over backwards to get checkboxes and the hidden multiselect synced up, all I had to do was create some models, some views and tell them how they are connected.

This is how the field itself is created

$multiselect . find ( "option" ) . each ( function ( i , el ) { var $el = $ ( el ) ; checkboxes . add ( new Checkbox ( { value : $el . val ( ) , label : $el . html ( ) , selected : $el . attr ( "selected" ) , } ) ) ; } ) ;

And to make sure data is synced up between its three representations (multiselect, visual checkboxes, the data structure itself), all it takes is this:

var Checkbox = Backbone . Model . extend ( { initialize : function ( ) { this . bind ( "change:selected" , this . toggled ) ; this . attributes . id = this . cid ; } , toggled : function ( ) { var $opt = $multiselect . find ( "option[value=" + this . get ( "value" ) + "]" ) ; if ( this . get ( "selected" ) ) { $opt . attr ( "selected" , "1" ) ; } else { $opt . removeAttr ( "selected" ) ; } } , } ) ;

Yep, that's the whole model and that's all it takes to sync everything up. Pretty cool huh? I remember trying to do this with just jQuery once ... I nearly stabbed my eyes out to end the misery.

All in all the whole thing is just 123 sloc, which can only mean one thing: Backbone is cool.

If you use my checkbox-field library, it's only going to be a single sloc for you:

$ ( "#my_selector" ) . checkboxField ( ) ;

That's it :)

Let me know what you think.

Did you enjoy this article? 👎 👍

Published on April 13th, 2012 in Checkbox, HTML, JavaScript, jQuery, Languages, Programming, Scripts, Uncategorized, User interface

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