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vue.jsvue-directives
Gustavo Dias
Gustavo Dias

Reputation: 3951

Difference between v-model and v-bind on Vue.js?

I'm learning Vue with an online course and the instructor gave me an exercise to make an input text with a default value.

I completed it using v-model but, the instructor chose v-bind:value, and I don't understand why.

Can someone give me a simple explanation about the difference between these two and when it's better use each one?

Upvotes: 382

Views: 235876

Answers (6)

bbsimonbb
bbsimonbb

Reputation: 28982

From here - Remember:

<input v-model="something">

is essentially the same as:

<input
    v-bind:value="something"
    v-on:input="something = $event.target.value"
>

or (shorthand syntax):

<input
    :value="something"
    @input="something = $event.target.value"
>

So v-model is a two-way binding for form inputs. It combines v-bind, which brings a js value into the markup and v-on:input to update the js value. The js value must be present in your data, or in an inject.

Use v-model when you can. Use v-bind/v-on when you must :-) I hope your answer was accepted.

v-model works with all the basic HTML input types (text, textarea, number, radio, checkbox, select). You can use v-model with input type=date if your model stores dates as ISO strings (yyyy-mm-dd). If you want to use date objects in your model (a good idea as soon as you're going to manipulate or format them), do this.

v-model has some extra smarts that it's good to be aware of. If you're using an IME ( lots of mobile keyboards, or Chinese/Japanese/Korean ), v-model will not update until a word is complete (a space is entered or the user leaves the field). v-input will fire much more frequently.

v-model also has modifiers .lazy, .trim, .number, covered in the doc.

Upvotes: 686

shafikul-stackoverflow
shafikul-stackoverflow

Reputation: 21

VUE JS
Problem => Unnecessary value binding used alongside v-model. It will interfere with v-model's behavior. 

<input v-model="signup.password" id="password" name="password" type="password" required="" value="">

It is problem.

Solve:

<input v-model="signup.password" id="password" name="password" type="password" required="">

Value cannot be used here if v-model is used. Removing the value will solve the problem

Upvotes: 1

Madmadi
Madmadi

Reputation: 2140

In simple words:

v-model: two way bindings

if you change input value, the bound data will be changed and vice versa.

v-bind:value one way binding

You can change input value by changing bound data but you can't change bound data by changing input value through the element_.

Check out this simple example: https://jsfiddle.net/gs0kphvc/

Upvotes: 100

sda87
sda87

Reputation: 402

v-model is for two way bindings means: if you change input value, the bound data will be changed and vice versa. But v-bind:value is called one way binding that means: you can change input value by changing bound data but you can't change bound data by changing input value through the element.

v-model is intended to be used with form elements. It allows you to tie the form element (e.g. a text input) with the data object in your Vue instance.

Example: https://jsfiddle.net/jamesbrndwgn/j2yb9zt1/1/

v-bind is intended to be used with components to create custom props. This allows you to pass data to a component. As the prop is reactive, if the data that’s passed to the component changes then the component will reflect this change

Example: https://jsfiddle.net/jamesbrndwgn/ws5kad1c/3/

Upvotes: 10

Vincent Tang
Vincent Tang

Reputation: 4160

There are cases where you don't want to use v-model. If you have two inputs, and each depend on each other, you might have circular referential issues. Common use cases is if you're building an accounting calculator.

In these cases, it's not a good idea to use either watchers or computed properties.

Instead, take your v-model and split it as above answer indicates

<input
   :value="something"
   @input="something = $event.target.value"
>

In practice, if you are decoupling your logic this way, you'll probably be calling a method.

This is what it would look like in a real world scenario:

<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>

<div id="app">
  <input :value="extendedCost" @input="_onInputExtendedCost" />
  <p> {{ extendedCost }}
</div>

<script>
  var app = new Vue({
    el: "#app",
    data: function(){
      return {
        extendedCost: 0,
      }
    },
    methods: {
      _onInputExtendedCost: function($event) {
        this.extendedCost = parseInt($event.target.value);
        // Go update other inputs here
    }
  }
  });
</script>

Upvotes: 2

Prashant Gurav
Prashant Gurav

Reputation: 79

v-model
it is two way data binding, it is used to bind html input element when you change input value then bounded data will be change.

v-model is used only for HTML input elements

ex: <input type="text" v-model="name" >

v-bind
it is one way data binding,means you can only bind data to input element but can't change bounded data changing input element. v-bind is used to bind html attribute
ex:
<input type="text" v-bind:class="abc" v-bind:value=""> 

<a v-bind:href="home/abc" > click me </a>

Upvotes: 7

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