How to create a method call from a string without using eval

Question

Can anyone advise me how to create a method call using a string and without using eval? Please note that methodCall cannot be hard-coded and has to be dynamic. methodCall will be created dynamically.

In the following example this refers to a Backbone view, e.g.

var amount = this.model.get('amount');

var $amount = this.$el.find('.amount');

var methodCall = 'this.parentController.parentController.addBinding';

//then need to call the method with args

methodCall('amount',$amount);

I first thought this would work:

this['controller']['parentController']['view']['addBinding'](amount, $amount);

However I came to realise that this would not be dynamic either. Does anyone have a solution?

There is nothing wrong with eval as long as you can be sure about what the string you are evaluating contains. — The Internet
– The Internet, Commented Dec 16, 2013 at 8:58
I am in middle of creating a framework which is based on Marionette & Backbone. Also I am using Stickit for two way data binding. System architecture supports child views to access parent model attributes. In view layer developer can call like parent.amount which will bind data to parent model of the particular view. Likewise user should be able to access like patent.parent.amount. I am coming from Angular background and badly missing $scope and Prototypal inheritance. In above example this is refer to a backbone view. — fernando
– fernando, Commented Dec 16, 2013 at 9:38
@Qantas94Heavy Yes. Always reference start from current backbone view. Therefore this will be always the the top object. — fernando
– fernando, Commented Dec 16, 2013 at 20:01

Community · Accepted Answer · 2017-05-23 12:03:44Z

2

As noted in this answer, Multiple level attribute retrieval using array notation from a JSON object, you can traverse the hierarchy of objects with something like this:

function findprop(obj, path) {
    var args = path.split('.'), i, l;

    for (i=0, l=args.length; i<l; i++) {
        if (!obj.hasOwnProperty(args[i]))
            return;
        obj = obj[args[i]];
    }

    return obj;
}

You could then give your view/model/collection a method to apply an arbitrary path:

var V = Backbone.View.extend({
    dyncall: function(path) {
        var f = findprop(this, path);
        if (_.isFunction(f))
            return f.call(this, 'your args');
    }
});

var v = new V();
v.dyncall('parentController.parentController.addBinding');

And a demo http://jsfiddle.net/nikoshr/RweEC/

A little more flexibility on passing the arguments :

var V = Backbone.View.extend({
    dyncall: function() {       
        var f = findprop(this, arguments[0]);
        if (_.isFunction(f))
            f.apply(this, _.rest(arguments, 1));
    }
});

var v = new V();
v.dyncall('parentController.parentController.addBinding', 'your arguments', 'another arg');

http://jsfiddle.net/nikoshr/RweEC/1/

edited May 23, 2017 at 12:03

CommunityBot

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answered Dec 17, 2013 at 8:56

nikoshr

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2 Comments

Qantas 94 Heavy Over a year ago

What about properties with . in them, e.g. random['.kkkk']? Still, nice answer :)

nikoshr Over a year ago

@Qantas94Heavy Use a different separator when building the path, something like parentController!parentController!addBinding for example and modify findprop accordingly

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