There are three main ways to bind Vue: interpolation expression, v-model and v-bind. 1. Interpolation expression ({{ }}) is used for text content display, such as {{ username }}, which will be automatically updated with data changes; 2. v-model implements two-way binding of form input, such as to keep the input box synchronized with the data; 3. v-bind dynamic binding attributes, such as: src binding image address. Responsive data needs to be defined in data, new attributes need to be added with the $set method, and array operations need to be pushed/pop and other methods. Pay attention to the type when binding values. For example, v-model.number ensures that the input is a number, and class binding requires a Boolean value. Mastering these details can make data binding more intuitive and efficient.

Vue's data binding method is actually not that complicated. If you understand several common methods clearly, you can basically deal with most development scenarios. It mainly revolves around a responsive system, and the core is to automatically reflect data changes on the view.

Three common ways of data binding

In Vue, there are three most common data binding methods: interpolation expression, v-model, and v-bind.

• Interpolation expression ({{ }})
  The simplest and most direct binding method is often used for text content display. For example, display the username:

   <p>Welcome, {{ username }}</p>

  When username changes, the content on the page will be automatically updated.

• v-model
  It is mainly used for form input elements and realizes two-way binding. That is to say, when the content of the input box changes, the data will be updated synchronously, and vice versa.

   <input v-model="message" />
  <p>{{ message }}</p>

  This way the input box and the text below will always be consistent.

• v-bind
  Used to dynamically bind attributes, such as class names, styles, src, etc. For example, dynamically set the image address:

   <img  src="/static/imghw/default1.png"  data-src="imageUrl"  class="lazy"  v-bind: / alt="Explain Vue data binding methods?" >

  Or abbreviated as:

   <img  src="/static/imghw/default1.png"  data-src="imageUrl"  class="lazy"  : / alt="Explain Vue data binding methods?" >

These methods can basically meet most data linkage needs.

Key points of responsive data updates

Vue is based on a responsive system, so the data must be "traceable" to trigger view updates.

• The data defined in data is responsive by default;
• If you want to add new attributes to the object and cannot directly assign values, you must use this.$set(obj, key, value) to ensure that it is responsive;
• There are also restrictions on array operations. Methods such as push() and pop() will be intercepted by Vue and triggered updates, but directly modifying the array content through the index will not take effect.

For example:

 data() {
  return {
    user: {
      name: 'Tom'
    }
  }
}

If you want to add an age property and make it responsive, this won't work:

 this.user.age = 25; // non-responsive

You should use $set :

 this.$set(this.user, 'age', 25); // Correct

Pay attention to type issues when binding values

Sometimes you may encounter situations where the value is clearly bound but the effect is incorrect. At this time, you should pay attention to whether the type passed is correct.

For example, the following example:

 <input type="number" v-model.number="age" />

After adding the .number modifier here, the entered value will be automatically converted to a numeric type instead of a string.

For example:

 <div :class="{ active: isActive }"></div>

If isActive is the string 'false' , it will actually be treated as true (because the non-empty string is the true value), then you should pay attention to the Boolean value being passed in.

Basically that's it. Mastering these binding methods and the small details behind them, Vue's data binding is actually quite intuitive. Not complicated, but it is easy to ignore some key points, especially the responsive mechanism.

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