Using the $.proxy command in javascript/jquery

Question

I have a bit of code that has a bit of a foreign syntax to me:

$.widget('ui.filterFieldDisplay', $.ui.fieldDisplay, {
setFoo: function() {
  .
  .
  .
  // added the next two lines
  var fooFieldWidgetOptions = fooFieldOptions.widgetOptions;
  fooFieldWidgetOptions['default'] = operator;
  var fooChangeProxy = $.proxy(this.fooChange, this);
  fooFieldWidgetOptions.changeCallback = fooChangeProxy;
}

fooChange: function(fooModel) {
  fooModel.getValue('bar');
  .
  .
  .
}

});

Is fooModel in this case referenced to the this pointer?

I know that the $.proxy method binds the this pointer to the function, so that it operates within that context. But I know that this doesn't get referenced to fooModel. So my question is: what is fooModel and where does it come from?

i assume the .'s is just your way of saying there's code there that you've omitted? — user400654
– user400654, Commented Apr 15, 2014 at 21:16

user400654 · Accepted Answer · 2014-04-15 21:43:33Z

1

No, fooModel will be whatever was passed as the first parameter to fooFieldWidgetOptions.changeCallback

fooFieldWidgetOptions.changeCallback("helloWorld!"); // fooModel will be `helloWorld!`

All $.proxy() did was ensure that this inside of fooChange will be the same as this inside of setFoo

edited Apr 15, 2014 at 21:43

answered Apr 15, 2014 at 21:20

user400654

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3 Comments

tomato Over a year ago

Since, nothing was passed to fooFieldWidgetOptions.changeCallback, does that mean fooModel is undefined? Is it set to a default value?

user400654 Over a year ago

If it is indeed the case that nothing is passed to it, yes, you haven't included that part of your code in your question though so i can't be sure.

tomato Over a year ago

Okay, so is that the only way to pass a variable to fooChange in my case? Is there other ways? I've edited my code to include more details about how it was called in setFoo.

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