Converting plain javascript hash into proper object

Question

I need to add some more OO flavor to my pure JS objects. Basically, I have on the server side

class Superitem {
    List<Item> items;
    Whatever whatever;
}

class Item {
    List<Subitem> subitems;
    Whatever whatever;
}

class Subitem {
    List<Whatever> whatevers;
}

In the client, I get a superitem as a plain Javascript hash and would like to convert it to something better. I started like

 Superitem(plain) {
      this.items = plain && plain.items || [];
      this.whatever = new Whatever(plain.whatever);
 }

but it's too verbose (my real classes are more complicated) and I rather doubt if its worth the effort. I'm not trying to mimic Java in Javascript, just want to add a few useful methods. Is there a better way? Thing like $.extend seem to be useless here.

icktoofay · Accepted Answer · 2014-06-29 00:41:43Z

1

$.extend is hardly useless. You could define the constructor[s] like so:

function Superitem(data) {
    $.extend(this, { items: [] }, data);
    this.whatever = new Whatever(this.whatever);
}

$.extend will inject into this first the defaults ({ items: [] }) and then the plain object provided to the function. It then converts whatever to a Whatever.

answered Jun 29, 2014 at 0:41

icktoofay

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6 Comments

maaartinus Over a year ago

This sounds good, except that in the later steps I will possibly garble the original data (which may be needed somewhere). I guess making a deep copy of data at the very beginning solves it.

icktoofay Over a year ago

@maaartinus: Note that going through the structure, converting everything to an instance of one of your classes is a deep copy. In this case, since we didn’t touch items besides bringing it over, it isn’t a deep copy, but since we touched whatever, changing it would not affect the original data.

maaartinus Over a year ago

Yes, but this assumes I don't forget anything. As the next step I have to do something like var self = this; $.each(self.items, function(i,v) {self.items[i] = new Item(v);}, right? And check for hasOwnProperty, right?

icktoofay Over a year ago

@maaartinus: Indeed, it assumes you don’t forget anything. Doing a deep copy first would be safer. Case in point: you’d need to use map rather than $.each. If you put a if(!(this isinstance Item)) return new Item(data); at the top of the definition of Item, you could then rewrite that line as this.items = this.items.map(Item);. I don’t see where hasOwnProperty comes in if you’re providing defaults.

maaartinus Over a year ago

I mentioned hasOwnProperty because of $.each iterating over everything and I don't want to add any garbage.

|

Jeremy J Starcher · Accepted Answer · 2014-06-29 00:44:19Z

0

Object hashes as you say are already regular, normal objects.

jQuery's extend method works if you are trying to merge multiple properties/methods, but it isn't needed.

// Create an object through JSON, just to show its a regular
// object.
var obj = JSON.parse('{"prop" : true}');
obj.method = function() {alert(this.prop)};

obj.method();

answered Jun 29, 2014 at 0:44

Jeremy J Starcher

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3 Comments

maaartinus Over a year ago

But I don't want to add the method directly to all instances. This makes debugging much worse as the methods obfuscate the content.

Jeremy J Starcher Over a year ago

Then you'll have to update your question and let us know what you are trying to add methods to.

maaartinus Over a year ago

To the prototype. That's why I need to create the object via the constructor... at least I think so. Sorry for being imprecise.

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