Background

I recently received a requirement in a Vue 3 low-code project to load remote components. These remote components have unpredictable names and are stored in a database. I need to fetch all component data through an API to determine what components are available. After research, I found two viable solutions to meet this requirement.

HTML File + UMD Components

This is the simplest solution to implement. We just need to package the component in UMD format and use it directly in the HTML file.

<div id="app">
    <test-input></test-input>
</div>
<script src="https://unpkg.com/vue@3/dist/vue.global.js"></script>
<script>
    // Load the component by mounting the script tag and access it through the window object
    await loadScript('http://localhost/component/input/0.1.0/bundle.js')
    app.component('TestInput', window.TestInput)
</script>

However, this solution is not suitable for large projects due to its low efficiency.

Vue 3 Project + ESM/UMD Components

This is the solution I implemented in my low-code project. During my research, I encountered and solved two main problems. Here's how it works:

Problem 1: Relative References

Since our project doesn't need to be compatible with IE, we can package the source code in ESM format. For example:

import { reactive } from 'vue'
// other code...

then use in project:

const { default: TestInput } = await import('http://localhost/component/input/0.1.0/bundle.mjs')

When loading the remote TestInput component as shown above, it causes a "Relative references must start with either '/', './', or '../'" error. This is because browsers don't support directly using import { reactive } from 'vue' - we need to change 'vue' to https://..../vue.js or './vue.js'. Usually, we don't need to worry about this as our build tools handle it automatically.

Problem 2: Different Vue 3 Contexts

My first attempt to solve the first problem was to package the component with all its dependencies. While this removed all import statements, it unfortunately didn't work. This is because the Vue 3 context in our project and the Vue 3 context from node_modules are incompatible - they need to share the same context to work properly.

Even though all Vue 3 method names are the same across different contexts, their variables are not. This prevents remote components from loading normally.

Solution

To solve these problems:

1. We can replace import { reactive } from 'vue' with const { reactive } = Vue to avoid the relative references error.
2. We can import the entire Vue 3 instance in main.js instead of packaging it with the source code. This ensures our project and remote components use the same Vue context.

To handle the code transformation, I created a rollup plugin called rollup-plugin-import-to-const (supporting both vite and rollup). It automatically transforms code from import { reactive } from 'vue' to const { reactive } = Vue. With these solutions in place, we can load remote components in our project:

const { default: TestInput } = await import('http://localhost/component/input/0.1.0/bundle.mjs')

Actually, we can load components in any format (ESM/UMD/CJS, etc.) as long as we solve these two problems.

Summary

Loading remote components isn't limited to these two solutions. For example, we can also use vue3-sfc-loader or webpack5 Module Federation. The choice depends on your project's specific requirements.

Generally, loading remote components is most commonly used in low-code platforms.