How to use JavaScript in vue

With the wide application and popularity of Vue, more and more developers have begun to involve the use of JavaScript in Vue. This article will introduce the usage methods and techniques of JavaScript in Vue, helping readers quickly master the skills of using JavaScript for Vue development.

1. Basic knowledge of using JavaScript in Vue

Vue is a JavaScript framework, so JavaScript is inseparable when using Vue. The JavaScript language of ES6 and above is mainly used in Vue. ES6 adds many new syntax and features to JavaScript, such as arrow functions and template strings.

In addition, Vue also has a core concept - Vue instance. Vue instance is created through the Vue constructor and can be understood as a Vue component. JavaScript code can be used in Vue instances to implement various functions.

2. Ways to use JavaScript in Vue

There are several ways to use JavaScript in Vue:

1. Use JavaScript expressions directly in Vue templates

Vue templates support the direct use of JavaScript expressions in templates and will render data in real time. For example:

<div>{{ message }}</div>

At this time, Vue will render the value of the message variable into the div in the template.

2. Define methods and calculated properties in the Vue instance

Many methods and calculated properties can be defined in the Vue instance, for example:

var vm = new Vue({
  el: '#app',
  data: {
    message: 'Hello Vue!'
  },
  methods: {
    greet: function () {
      alert('Hello ' + this.message + '!')
    }
  },
  computed: {
    reversedMessage: function () {
      return this.message.split('').reverse().join('')
    }
  }
})

In the above example, We define a method greet and a calculated property reversedMessage to return the reversed string of the message string. These methods and calculated properties can be called in the template through the instance name vm.

3. Use JavaScript code in the Vue life cycle hook function

Vue provides multiple life cycle hook functions. These hook functions will be automatically called during the life cycle of the instance. You can use the hook function to Write JavaScript code in the function to implement specific functions.

For example, define a variable in the created hook function:

var vm = new Vue({
  el: '#app',
  created: function () {
    this.count = 0;
  },
  methods: {
    addCount: function () {
      this.count++;
    }
  }
})

In the above example, we define a variable count in the created hook function and increment it each time in the addCount method 1. This variable can be accessed in the template through the count variable in the instance.

3. Common functions of JavaScript in Vue

In Vue, we can use JavaScript to achieve many functions. Some common functions are listed below:

1. Get DOM elements

Using JavaScript, you can obtain DOM elements, and you can save the data in the DOM elements to the Vue instance through Vue's responsive mechanism. For example:

var vm = new Vue({
  el: '#app',
  data: {
    message: ''
  },
  methods: {
    showMessage: function () {
      alert('you input is:' + this.message);
    }
  },
  mounted: function () {
    var input = document.getElementById('messageInput');
    input.addEventListener('input', function (event) {
      vm.message = event.target.value;
    })
  }
})

In the above example, we obtained the DOM element with ID messageInput in the mounted hook function and added an event listener. When the user enters data, the event is triggered and the entered data is saved to In the message of the Vue instance.

2. Binding events

Use the v-on directive in Vue to bind event handlers, for example:

<button v-on:click="increment">+</button>

In the above example, we use v- The on directive binds the click event, and the increment method is triggered when the user clicks the button.

3. Loop rendering list

In Vue, you can use the v-for instruction to loop the rendering list, for example:

<ul>
  <li v-for="item in items">{{ item }}</li>
</ul>

In the above example, we use v- The for instruction loops through the rendering list and renders each element in items as a li element.

4. Conditional rendering

In Vue, you can use the v-if and v-else instructions to implement conditional rendering, for example:

<div v-if="show">
  <p>{{ message }}</p>
</div>
<div v-else>
  <p>It is hidden now.</p>
</div>

In the above example, we Use the v-if directive to determine the value of the show variable. If show is true, the first div is rendered, otherwise the second div is rendered.

4. Summary

Using JavaScript in Vue will make our code more flexible and efficient. By learning the methods and techniques introduced in this article, we can better understand the importance and usage of JavaScript in Vue, thereby improving our efficiency and proficiency in Vue development.

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