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?

• user400654: i assume the .'s is just your way of saying there's code there that you've omitted?
• tomato: Yes, the . is omitted code for the sake of secrecy.

Answer 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

• tomato: Since, nothing was passed to fooFieldWidgetOptions.changeCallback, does that mean fooModel is undefined? Is it set to a default value?
• user400654: 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: 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.