How to build a namespace-like string using chained variables

Question

This is a strange one, but I'm exploring it to see if it's possible.

Let's say that I have a .NET application where I am using PubSub. I want a way to define the topic string using chained objects (not functions). The goal is to allow me a way of defining strings that lets me to take advantage of Visual Studio's IntelliSense and reduce the likelihood of spelling errors.

Here's an example:

/* Manual way */
var topic = "App.Navigation.CurrentItem"



/* Desired Solution */

// ... define the objects here ...

var topic = App.Navigation.CurrentItem;
console.log(topic); // "App.Navigation.CurrentItem"

var topic2 = App.Footer.CurrentItem;
console.log(topic2); // "App.Footer.CurrentItem"

I'd like each object to be responsible for outputing it's own value, and have the chaining process responsible for joining itself to the previous chained object via a predefined separator (in my case, a period [.]).

I've been playing with JavaScript getter syntax, but I'm curious if there's a better way.

Has anyone done something like this before, and if so, how did you solve it?

Why do you want the chaining process to be responsible for building the string? Why not have code that just says `App.Navigation.CurrentItem = "App.Navigation.CurrentItem"`? — StriplingWarrior, Oct 05 '15 at 21:19
My job is R&D, so I'm always trying to find ways to make things easier for my team. Being able to define a variable to always return one value, regardless of its position in a chain, keeps my code DRY. It's honestly not a need to have. I'm just curious if anyone has a way to use JS to do it. — Travis Wilson, Oct 06 '15 at 15:36

score 1 · Accepted Answer · answered Oct 06 '15 at 16:00

You're requirements aren't totally clear to me, but are you looking for something like this?

function namespace(ns) { this._ns = ns; }
namespace.prototype.toString = function() {return this._ns};
namespace.prototype.extend = function(suffix) {
    return new namespace(this._ns + "." + suffix)
};

Usage:

App = new namespace('App');
App.Navigation = App.extend('Navigation');
App.Navigation.CurrentItem = App.Navigation.extend('CurrentItem');
console.log(App.Navigation.CurrentItem.toString()); // "App.Navigation.CurrentItem"

This works perfectly - you nailed it! I wouldn't have thought to go this simple. Makes total sense, and you've taught me something here. Hug thanks! — Travis Wilson, Oct 06 '15 at 16:02

score 0 · Answer 2 · answered Oct 06 '15 at 17:04

This is what I ended up with after reviewing StriplingWarrior's answer:

function Namespace(name, config) {
    if (typeof name === "object") {
        config = name;
        name = null;
    }
    config = config || {};

    this._ns = name;
    this.define(config);
}
Namespace.prototype.toString = function() { return this._ns };
Namespace.prototype.define = function(config, base) {
    base = base || this;

    for (key in config) {
        var name = (base._ns) ? base._ns + "." + key : key;
        base[key] = new Namespace(name);
        base.define(config[key], base[key]);
    }

    return base;
};

Usage:

var App = new Namespace("App", {
    Navigation: {
        Items: {
            Current: {}
        }
    },
    Content: {},
    Footer: {
        Items: {
            Current: {}
        }
    }
});

console.log(App.toString()); // App
console.log(App.Navigation.Items.Current.toString()); // App.Navigation.Items.Current
console.log(App.Footer.toString()); // App.Footer

I also wrote a convenience method to reduce the toString():

function NS(namespace) {
    return namespace.toString();
}

console.log(NS(App.Navigation.Items.Current));

Thanks again to StriplingWarrior for the the help!

How to build a namespace-like string using chained variables

2 Answers2