Vue.js—Difference between v-model and v-bind

问题

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?

回答1:

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.

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.

回答2:

In simple words 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.

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

回答3:

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>

回答4:

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>

来源：https://stackoverflow.com/questions/42260233/vue-js-difference-between-v-model-and-v-bind

标签

javascript

mvvm

frameworks

Vue.js

frontend