One-way data binding in vanilla JS (POC)

Code and Demo

Let's break it down in small pieces

I assume you are already familiar with data-binding.

Most of the modern front-end frameworks offer data-binding out of the box, just ready to use, but what there is under the hood?

I tried to implement a basic version of one-way data binding and it was really fun :)

So, what do we need to have one-way data binding?

• A view, in our example HTML.
• A state, kept in memory with JavaScript.

The Key feature is:

Everytime the state changes, the view need to be updated

So let's assume we have an HTML view:

    <div data-binding="quote"></div>

and a state:

    const state = {
      quote: 'Either you run the day, or the day runs you.'
    };

We can easily set the view the first time:

    document.querySelector('[data-binding="quote"]').innerHTML = state.quote

We want some magic, so that when we update the state:

    state.quote = 'We become what we think about'

the view should magically change. To achieve this, we could modify the default behaviour of the set property for the state object, so that other than update the model, it would also update our view.

One way to do that in JavaScript is using the Proxy Object:

    const createState = (state) => {
      return new Proxy(state, {
        set(target, property, value) {
          target[property] = value; // default set behaviour
          render(); // updates the view everytime the state changes
          return true;
    }
      });
    };

    const state = createState({
      quote: 'Either you run the day, or the day runs you.' // creates initial state
    });

With the power of the Proxy everytime we update our state, the render function will be called.
A possible implementation of render can be:

    const render = () => {
     document.querySelector('[data-binding="quote"]').innerHTML = state.quote
    };

Now if we modify the state with:

    state.quote = 'We become what we think about.'

The render function will be called and the view will update! MAGIC! 👨‍💻