2 way data binding in JavaScript

Question

Two-way data binding refers to the ability to bind changes to an object’s properties to changes in the UI, and vice-versa.

Can we achieve 2-way data-binding with JavaScript?

Especially 2 Way Data Binding without Frameworks.

Answer 1

When an input is changed update the value, add a setter to the value which sets the inputs content. E.g this element:

<input id="age">

And some js:

var person = (function(el){
 return {
   set age(v){
    el.value = v;
   },
   get age(){
     return el.value;
   }
 };
})(document.getElementById("age"));

So you can do:

 person.age = 15;

And the input will change. Changing the input changes person.age

Answer 2

Yes, we can achieve the two way data binding using pure javascript.

twoWay=function(event) {
  var elem = document.getElementsByClassName(event.currentTarget.className);
  for(var key in elem){
    elem[key].value=event.currentTarget.value;
  }
}

You can check the jsfiddle.

Answer 3

Simple and working approach to two-way binding, only using vanilla JS.

<!-- index.html -->
<form action="#" onsubmit="vm.onSubmit(event, this)">
    <input onchange="vm.username=this.value" type="text" id="Username">
    <input type="submit" id="Submit">
</form>
<script src="vm.js"></script>

// vm.js - vanialla JS
let vm = {
    _username: "",
    get username() {
        return this._username;
    },
    set username(value) {
        this._username = value;
    },
    onSubmit: function (event, element) {
        console.log(this.username);
    }
}

JS Getters and Setters are quite nice for this - especially when you look at the browser support.