Render functions provide a low-level method of defining Vue.js components. They allow you to work directly with the virtual DOM. In this article, learn how to wield them to your advantage.
Daniel Kelly
October 14, 2024
Vue.js is known for its intuitive template-based approach to building user interfaces. However, for more complex scenarios, Vue offers a powerful alternative: render functions. These JavaScript functions provide a lower-level, more flexible way to create Vue components and are ultimately what your SFC’s compile too. For the Senior Vue.js Developer Exam, you’ll need to know how to work with render functions.
While templates are excellent for most use cases, render functions offer several advantages:
However, templates are generally more readable and easier to maintain for most components.
A basic render function looks like this:
import { h } from "vue"
function MyComponent(props, { slots, emit, attrs }) {
return h("div", "Hello World!")
}
The h
function (short for hyperscript) is the key to creating elements. It accepts three arguments:
Render functions work directly with the Virtual DOM. Instead of writing HTML, you use JavaScript to describe the structure of your component. Vue then uses this description to efficiently update the actual DOM when changes to reactive data occur. Take a look at this simplified example of virtual DOM. Notice how it describes a DOM node but via a JS object:
const vnode = {
type: 'div',
props: {
id: 'hello'
},
children: [
/* more vnodes */
]
}
It’s actually pretty simple!
Render functions are particularly useful for:
Here's an example of a render function with a type prop, and a default slot. It creates a heading component that outputs h1
- h6
tags that have slugified id’s based on the heading content. When a heading is clicked, the url updates with the proper hash and the url is copied to the clipboard.
import { h } from "vue";
import slugify from "slugify";
export default (props, { slots }) => {
const id = slugify(slots.default().at(0).children, {
strict: true,
}).toLowerCase();
return h(
props.type || "h1",
{
id,
onClick: () => {
navigator.clipboard.writeText(
window.location.href.replace(/#.*/, "") + `#${id}`,
);
},
},
[h("a", { href: `#${id}`, class: "no-underline" }, slots.default())],
);
};
Render functions in Vue.js offer a powerful way to create complex, dynamic components. While they have a steeper learning curve compared to templates, understanding how they work can give you a slight edge and truly elevate you to a senior Vue.js developer. Prove your knowledge on Vue.js render functions, provide/inject, unit testing, and more by taking the Senior Vue.js Developer Exam and show employers that you are a master of Vue.js!
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