declaration vue 3 variables

How to Declare Variables in Vue 3

When working with Vue 3, there are several ways to declare variables. These variables are used to store data that can be accessed and manipulated throughout your application.

1. Using the 'data' Option

The most common way to declare variables in Vue 3 is by using the 'data' option. This option is used to declare an object that contains all the variables you want to use in your component.

<div id="app">
  <!-- Declare data object -->
  <script>
    const app = Vue.createApp({
      data() {
        return {
          message: 'Hello, World!'
        }
      }
    })
    app.mount('#app')
  </script>

  <!-- Access variable in template -->
  <h1>{{ message }}</h1>
</div>

In this example, we declare a data object that contains a variable called 'message' with the value 'Hello, World!'. Within the template, we use double curly braces to access and display the value of the 'message' variable.

2. Using the 'computed' Option

The 'computed' option is used to declare variables that are computed based on other variables. This option is useful if you have complex calculations that need to be performed.

<div id="app">
  <!-- Declare computed variable -->
  <script>
    const app = Vue.createApp({
      data() {
        return {
          basePrice: 10,
          discount: 0.2
        }
      },
      computed: {
        finalPrice() {
          return this.basePrice * (1 - this.discount)
        }
      }
    })
    app.mount('#app')
  </script>

  <!-- Access variable in template -->
  <h1>{{ finalPrice }}</h1>
</div>

In this example, we declare a computed variable called 'finalPrice' that is calculated based on the 'basePrice' and 'discount' variables. Within the template, we use double curly braces to access and display the value of the 'finalPrice' variable.

3. Using the 'props' Option

The 'props' option is used to declare variables that are passed down from a parent component to a child component. This option is useful if you have components that need to share data with each other.

<!-- Parent component -->
<div id="app">
  <child-component message="Hello, World!"></child-component>
</div>

<script>
  const app = Vue.createApp({})
  app.component('child-component', {
    props: {
      message: String
    },
    template: '<h1>{{ message }}</h1>'
  })
  app.mount('#app')
</script>

In this example, we declare a child component that receives a 'message' variable from its parent component. Within the child component's template, we use double curly braces to access and display the value of the 'message' variable.

These are just a few ways to declare variables in Vue 3. Depending on your specific use case, you may find other options that work better for you.