Vue.js Single File Components: A Comprehensive Guide

In this article, we will explore how Vue.js simplifies the process of creating a single file responsible for all aspects of a component. By centralizing the responsibility for appearance and behavior, Vue.js offers a convenient approach known as Single File Components.

Traditionally, a Vue component can be declared in a JavaScript file (.js) using the Vue.component method or within a new Vue instance. However, Vue.js introduces a new file format called .vue that revolutionizes component development by allowing the integration of JavaScript logic, HTML code templates, and CSS styling in a single file.

Let’s take a look at an example of a Single File Component:

<template>
 <p>{{ hello }}</p>
</template>

<script>
export default {
 data() {
 return {
 hello: 'Hello World!'
 }
 }
}
</script>

<style scoped>
 p {
 color: blue;
 }
</style>

Thanks to the use of Webpack, Single File Components are fully supported in Vue CLI, making it incredibly easy to work with them. However, it’s important to note that .vue files require a webpack setup and are primarily designed for full-blown single-page applications (SPAs).

One of the advantages of Single File Components is that they leverage the power of modern web features out-of-the-box. You have the flexibility to use preprocessors such as TypeScript, SCSS, Sass, Less, PostCSS, and Pug for your CSS, template, and JavaScript. Additionally, you can utilize modern JavaScript (ES6-7-8) using Babel integration and ES Modules.

To ensure CSS encapsulation within a Single File Component, you can simply add the scoped attribute to the <style> tag. This automatically assigns a unique class to the component, preventing CSS leakage to other components.

If your JavaScript logic becomes extensive, you can easily externalize it by using the src attribute:

<template>
 <p>{{ hello }}</p>
</template>
<script src="./hello.js"></script>

You can also externalize your CSS in the same manner:

<template>
 <p>{{ hello }}</p>
</template>
<script src="./hello.js"></script>
<style src="./hello.css"></style>

When declaring the data for a component, you have multiple options. You can use the data method as shown in the example above:

export default {
  data() {
    return {
      hello: 'Hello World!'
    }
  }
}

Alternatively, you can use data as a function:

export default {
  data: function() {
    return {
      name: 'Flavio'
    }
  }
}

Using an arrow function for data is also possible, but it can lead to issues when accessing component methods that rely on the this keyword. Therefore, it’s recommended to use regular functions instead of arrow functions in these cases.

Lastly, you may come across the CommonJS syntax when declaring components:

module.exports = {
  data: () => {
    return {
      name: 'Flavio'
    }
  }
}

Though functional, it’s advisable to use the ES Modules syntax, which is a standardized JavaScript format.

In conclusion, Vue.js Single File Components provide a streamlined approach to component development by consolidating JavaScript, HTML, and CSS code into a single file. With support for modern web features and integration with preprocessors, Single File Components make it easy to build robust and encapsulated Vue applications.