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Built-in modules

The WasmEdge QuickJS runtime supports ES6 and NPM modules for application developers. However, those approaches could be more convenient for system developers. They need an easier way to add multiple JavaScript modules and APIs into the runtime without using build tools like rollup.js. The WasmEdge QuickJS modules system allows developers to drop JavaScript files into a modules folder and have the JavaScript functions defined in the files immediately available to all JavaScript programs in the runtime. A good use case for this module's system is to support Node.js APIs in WasmEdge.

In this article, we will use the wasmedge-quickjs/modules as an example to showcase how to import NodeJS API or a third-party module.

Prerequisites​

See here

The modules system​

The modules system collects JavaScript files in the modules directory in the WasmEdge QuickJS distribution. To use the JavaScript functions and APIs defined in those modules, you need to map this directory to the /modules directory inside the WasmEdge Runtime instance. The following example shows how to do this on the WasmEdge CLI. You can do this with any of the host language SDKs that support the embedded use of WasmEdge.

wasmedge --dir /modules:/host/os/path/to/modules wasmedge_quickjs.wasm example_js/hello.js WasmEdge Runtime

Add your own JavaScript modules​

The module_demo shows how you can use the modules system to add your own JavaScript APIs. To run the demo, first copy the two files in the demo's modules directory to your WasmEdge QuickJS's modules directory.

cp example_js/module_demo/modules/* modules/

The two JavaScript files in the modules directory provide two simple functions. Below is the modules/my_mod_1.js file.

export function hello_mod_1() {
  console.log('hello from "my_mod_1.js"');
}

And the modules/my_mod_2.js file.

export function hello_mod_2() {
  console.log('hello from "my_mod_2.js"');
}

Then, just run the demo.js file to call the two exported functions from the modules.

import { hello_mod_1 } from 'my_mod_1';
import { hello_mod_2 } from 'my_mod_2';

hello_mod_1();
hello_mod_2();

Here is the command to run the demo and the output.

$ wasmedge --dir .:. wasmedge_quickjs.wasm example_js/module_demo/demo.js
hello from "my_mod_1.js"
hello from "my_mod_2.js"

Following the above tutorials, you can easily add third-party JavaScript functions and APIs to your WasmEdge QuickJS runtime.

We included JavaScript files to support Node.js APIs for the official distribution. You can use those files as further examples.