CODEWITHSUNDEEP
javascriptunderscore.js
onefootswill
onefootswill

Reputation: 4077

Binding This in a Nested Function with Underscore.js

I have a question with regards to the Bind feature in Underscore.js let’s say we have the following object "room": 

var person = 'Bob';

$(function () {

    var room = {
        capacity: 10,
        exits: 2,
        count: 0,
        person: '',
        addPerson: function (name) {
            this.count += 1;            

            var nestedFunction = function (nameOfPerson) {

                //  this is bound to window
                this.person = nameOfPerson;

            }(name);        
        }
    };

    room.addPerson('dave');
});

At the line indicated by my comment, "this" is bound to the window. That is expected behaviour.

Let’s say we want to bind it to the "room" object. Is it possible to do that with Underscore.js' bind method.

Note: I am aware I could handle this with the good old "that = this" routine. But I'm not interested in that.

Upvotes: 3

Views: 696

Answers (2)

Brent
Brent

Reputation: 2485

I know this might not help for the question but I stumbled on this question in regards to backbone.

I was trying to save one model then another on the call back. He is the working end result. But _.bind could be used in any other function you cant access this on. 

  this.information.set('name', 'Bob');
  this.information.save(null,
        {
            success: _.bind(function(model, response)
            {
                    console.log('Saved Information');
                    this.review.set('review', "This is a test Review");
                    this.review.save(null,
                    {
                            success: function(model, response)
                            {
                                console.log('Saved Review');
                                location.reload();
                            }
                    });
            }, this)

        });

Upvotes: 0

Niranjan Borawake
Niranjan Borawake

Reputation: 1638

Yes, you can definitely do this using Underscore's bind.

You can use bind this way:

CODE:

 var nestedFunction = _.bind(function (nameOfPerson) {
     this.person = nameOfPerson;
 },this);

Please take note of the this passed as a second argument to bind, which makes this refer to what you want and not window.

JSFIDDLE

You can also do this without Underscore's bind by using call.

CODE:

   addPerson: function (name) {
        this.count += 1;            
        var nestedFunction = function (nameOfPerson) {
            this.person = nameOfPerson;
        };        
        nestedFunction.call(this,'dave');
    }

JSFIDDLE

Upvotes: 3

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