Adding methods to methods in javascript

Question

I'm using Backbone, but I feel this is more of a general javascript syntax question.
How can I add a method inside a method (or a function inside a function) and call them by chaining both?

var myModel = Backbone.Model.extend({

    method1: function(x){
        method2: function(y){
            return x*y;
        }
    }

    // or perhaps
    method1: function(x){
        {
            method2: function(y){
                x = x*y;
            }
        }
        return x;
    }
});

var mymodel = new myModel();
mymodel.method1(3).method2(5); // outputs 15

netdigger · Accepted Answer · 2014-05-02 07:51:02Z

1

Usually the chaining is acheived by returning the original object.

var myModel = Backbone.Model.extend({
    methodSub: function(x){
        this.x -= x;
        return this;
    },
    methodAdd: function(y){
        this.y += y;
        return this;
    }
});

Or like this: (but then it's essentially another object and should be defined appropriately)

var myModel = Backbone.Model.extend({
    methodSub: function(x){
        this.x -= x;
        return {
             x : this.x,
/*           val : this.x, Or simply val, if that seems appropriate */
             methodAdd: function(y){
                this.x += y;
                return this;
             }
        }
    }
});

Don't know if any of them is the way you imagined. But in essence, you have to return something to chain something. Else the method will return undefined and you can't call a method "on" undefined.

edited May 2, 2014 at 7:51

answered May 2, 2014 at 6:27

netdigger

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5 Comments

Westerfaq Over a year ago

Not really. When I call method1 alone, it cannot return this. I need method1 to know wether method2 is chained after it.

netdigger Over a year ago

Dont think you can "know" if a method is chained after or not. But you could so something like (ill change the answer)

Westerfaq Over a year ago

That works great! But how can I return x when just calling mymodel.methodSub(3)?

netdigger Over a year ago

Dont know if theres a better way but you can add x : x in the map I guess. Ill update

Westerfaq Over a year ago

I'm not having any success with that :/

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