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Tiny Two-Way Data Binding

I wrote my own two-way data binding library, partly to experiment, partly to solve existing needs in my own projects - weighing in at < 2K compressed.

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Data binding to the DOM is just one of those things that's damn handy when you've got it and super laborious when you don't. The problem is that it usually comes at a price of a hefty framework (hefty can apply to byte-size, but more often: the learning curve to use said framework).

So, as any good re-inventer of wheels, I wrote my own two-way data binding library, partly to experiment, partly to solve existing needs in my own projects - weighing in at < 2K compressed.

I present (cleverly named): bind.js

Demo time

[Here] is an interactive demo of bind in action. As you change the state of the form, you'll see the object update on the right (a JSON.stringify output).

Example usage

The concept behind the API is fairly simple: take an object bind it to functions and/selectors given a particular mapping.

For example, to bind a score and player name to the DOM:

var user = Bind({
  name: '[new user]',
  game: { score: 0 }
}, {
  'game.score': 'span.score',
  name: 'input[name="username"]'
})

// in the game
user.game.score += 25;


...and the HTML updates take care of themselves. Then the user enters their name in the input field, it'll update the user object.

The mapping value is flexible too, and can be:

  • A string representing a selector
  • A function which receives the new value
  • An object that supports any of the following properties: dom, callback and transform

With an object as the value of the mapping, it allows you to do a transform on your data before it lands in the DOM. This is obviously useful for things like updating list elements:

var data = Bind({
  cats: ['nap', 'sam', 'prince']
}, {
  cats: {
    dom: '#cats',
    transform: function (value) {
      return '<li>I had a cat called <em>' + this.safe(value) + '</em></li>';
    }
  },
  'cats.0': {
    dom: '#first-cat',
    transform: function (value) {
      return 'My first cat was ' + this.safe(value);
    }
  }
});

Inside the transform function also has a helper, this.safe() which will escape your content safe for HTML.

Object.observe?

Nope. I'm not using it, which is also why there's some limitations (property deletion being the main/only one).

Why not? Mostly for a larger platform of support. This library supports IE9 upwards (and thus all other browsers) and includes feature detection.

I also tried an Object.observe polyfill early on, but didn't have much success (though I don't recall what the issues were). I also fancies the code challenge :)

HTML decorators?

Nope (again). I was recently debugging some Knockout code, and found myself struggling as I realised that the actual binding was happening in the HTML, and the manipulation was happening in the separate JavaScript file.

So no, there's no data-* support, intentionally. All the code lives in one place: in the JavaScript.

I personally like that my data binding is all in one place. If you're not so keen, there's always Angular, Knockout and the like.

Nice to haves

I've started opening a few issues on things I'd like, but they currently include:

  • Root object mapping support (i.e. to be able to hook a callback on anything changing)
  • Glob support, i.e. me.*.name will fire callbacks matching any path starting with me and ending with name
  • Test to test every individual form element (currently it's a bit of a mishmash)

Feel free to raise an issue or feature request or let me know if you'd use this even!



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Topics:
javascript ,json ,bind.js ,web dev ,html5

Published at DZone with permission of Remy Sharp, DZone MVB. See the original article here.

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