Generating Javascript from coffeescript equivalent to manual javascript in _.each underscore

Question

I have a code in Javascript as :

 _.each(this.collection.models, function (student) {
            $(this.el).append(new StudCloneItemView({ model: student }).el);
        }, this);

While I am writing This in coffescript as

_.each this.collection.models  , (student) => 
$(@el).append new Item ({ model:student }).el

which generates

_.each(this.collection.models, function(student) {
      return $(_this.el).append(new Item({
        model: student
      }.el));
    });

Which isn't desirable as per my requirement . The last segment of "this" element has been missing into the generated javascript . Its very important.

How would I generate The javascript as mentioned on top using the coffeescript I mentioned for _.each ????

Is there anyway to do that ?? Or am I missing any syntax ?

mu is too short · Accepted Answer · 2012-09-01 21:26:30Z

1

Your JavaScript:

_.each(this.collection.models, function (student) {
    $(this.el).append(new StudCloneItemView({ model: student }).el);
}, this);

and what your => CoffeeScript produces:

var _this = this; // This is somewhere above your _.each in the generated JS
_.each(this.collection.models, function(student) {
    return $(_this.el).append(new Item({
        model: student
    }.el));
});

are functionally equivalent. You don't need the context argument to _.each since the => generates an alias for this (called _this) that is used inside the callback.

As an aside, Backbone collections have various Underscore methods mixed in so you don't have to say _.each(@collection.models, ...), you can use each directly on the collection:

@collection.each (student) =>
    @$el.append(new StudCloneItemView(model: student).el)

I've also switched to the pre-built $el that your view already has, there's no need to build a new jQuery object on each iteration.

answered Sep 1, 2012 at 21:26

mu is too short

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1 Comment

Joy Over a year ago

yes I realised tht after your post . That was really helpful how underscore and coffeescript are mixed

Austin Greco · Accepted Answer · 2012-09-01 21:00:01Z

1

like this:

_.each @collection.models, ((student) ->
  $(@el).append new StudCloneItemView(model: student).el
), this

answered Sep 1, 2012 at 21:00

Austin Greco

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