Integrating JavaScript's .bind() with callback function

Question

So, below is a very barebones example of a case where I'd set that to this so I can use the scope of myObj. How would I integrate Function.prototype.bind, just so I can see how I can use it in the future?

var myObj = {

        specialFunction: function () {

        },

        anotherSpecialFunction(){

        },

        getAsyncData: function (cb) {
            // an operation
            cb();
        },

        render: function () {
            var that = this;
            this.getAsyncData(function () {
                that.specialFunction();
                that.anotherSpecialFunction();
            });
        }
    };

    myObj.render();

that would give the scope of render function in your case and not of myObj — Vandesh
– Vandesh, Commented Oct 7, 2013 at 14:50
Where is getAsyncData defined? Is it suppose to be myObj.getAsyncData? — Musa
– Musa, Commented Oct 7, 2013 at 14:52
@benhowdle89 : correct. My bad! Verified here - jsfiddle.net/FKduF :) — Vandesh
– Vandesh, Commented Oct 7, 2013 at 14:55

Musa · Accepted Answer · 2013-10-07 15:17:56Z

2

Just use bind on the method you want and specify the context

render: function () {
    this.getAsyncData(this.specialFunction.bind(this));
}

    render: function () {
        this.getAsyncData(someFunction.bind(this));
        function someFunction() {
            this.specialFunction();
            this.anotherSpecialFunction();
        }
    }

edited Oct 7, 2013 at 15:17

answered Oct 7, 2013 at 15:05

Musa

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1 Comment

benhowdle89 Over a year ago

That's cool. Maybe I made it too contrived. I've edited it to reflect what I'd be more likely to do in a real life use case.

Bergi · Accepted Answer · 2013-10-07 15:21:09Z

1

How would I integrate Function.prototype.bind

Omit that, use this instead and bind the function to the instance:

…
    render: function () {
        this.getAsyncData(function () {
            this.specialFunction();
            this.anotherSpecialFunction();
        }.bind(this));
    }
…

just so I can see how I can use it in the future?

You can use it right now. Every decent browser supports it, and if you really care about old Internet Explorers and the like you can shim it.

answered Oct 7, 2013 at 15:21

Bergi

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Comments

Anthony Grist · Accepted Answer · 2013-10-07 15:18:27Z

0

If you wanted this to still refer to myObj inside the callback function passed to getAsyncData you'd want your render function to look like this:

render: function () {
    this.getAsyncData((function () {
        this.specialFunction();
        this.anotherSpecialFunction();
    }).bind(this));
}

answered Oct 7, 2013 at 15:18

Anthony Grist

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