Assign function to variable and pass parameter

Question

I guess this is probably an easy problem, but I cannot figure it out myself (using the wrong search criteria?).

As the title says, I want to assign a function to a variable and pass a variable to that function like this:

function doStuff(control) {
    var myObj = {
        "smooth": false,
        "mouseup": function(value) {
            jQuery(_getSelectorStringFromControlId(control.id)).blur();
        }
    };
}

Now I want the control.id to be replaced with its actual value before the function is assigned to the mouseup variable.

So when control.id = 'myOwnId' then myObj.mouseup should be:

function(value) {
    jQuery(_getSelectorStringFromControlId('myOwnId')).blur();
}

How can this be accomplished?

hvgotcodes · Accepted Answer · 2011-11-03 14:17:59Z

3

this is the basic form for assigning a function to a variable

var myFunc = function(x) {
   console.log(x);
}

once that is done, you can invoke the function like so (passing in anything you want)

myFunc(1);

answered Nov 3, 2011 at 14:17

hvgotcodes

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1 Comment

Moolie Over a year ago

My problem wasn't that simple, when defining an anonymous function substituting a parameter with the value of a variable is more tricky. N3dst4 pointed me in the right direction

N3dst4 · Accepted Answer · 2011-11-03 19:44:15Z

2

I think what you're looking for here is a closure, which is where a function which remembers variables that were in scope when it was created ("control" in your case) but then gets called from elsewhere. In your example, you can return myObj from the doStuff function, and whenever you call mouseup() it will refer to the "right" value of control. So in fact, you're creating a closure in that example code already.

If you want to make the closure keep a reference to just the id, you could do this:

function doStuff(control) {
    var myId = control.id;
    var myObj = {
        "smooth": false,
        "mouseup": function(value) {
            jQuery(_getSelectorStringFromControlId(myId)).blur();
        }
    };
}

You can now have lots of copies of myObj floating round your page, and on each one, mouseup() will be using a different id.

More info on closures: https://developer.mozilla.org/en/JavaScript/Guide/Closures

As an aside, closures are the best thing ever for utterly astonishing people who've never done any functional programming.

answered Nov 3, 2011 at 19:44

N3dst4

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1 Comment

Moolie Over a year ago

Closures were the way to go, thanks. In fact I had the whole function assignment in a loop, so the 'Creating closures in loops: A common mistake' paragraph in the provided link gave me my solution.

Rob W · Accepted Answer · 2011-11-03 14:19:59Z

1

You will have to call:

var some_control = {id: "myOwnId"};
doStuff(some_control);

It creates an object using object literals, { }. Then, a property id is defined. This whole object is passed as a parameter to function doStuff.

answered Nov 3, 2011 at 14:19

Rob W

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Comments

buschtoens · Accepted Answer · 2011-11-03 19:11:18Z

0

function doStuff(control) {
    var myObj = {
        "smooth": false,
        "mouseup": function(value) {
            jQuery(_getSelectorStringFromControlId(control.id)).blur();
         }
    };
}

doStuff({id: "yourID"}); // works now

Test it on jsFiddle.

There's one problem left: You don't have access to the inner value parameter but I assume that you're going to bind this anonymous function to an event listener.

edited Nov 3, 2011 at 19:11

answered Nov 3, 2011 at 14:23

buschtoens

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