dynamically import class from file and use a function in it-CodePudding

i have this file ./src/commands/test.js:

export default class {
    run() {
        console.log('test!')
    }
}

i am trying to make a command that will get all commands in that folder and call their run function:

#! /usr/bin/env node

const fs = require('fs')
const folders = [
    './src/commands',
    //'./my_modules/diontron/unity/src/commands',
]

folders.forEach(folder => {
    fs.readdir(folder, (err, files) => {
        files.forEach(file => {
            if (file != 'index.js') {
                let commandClass = require(folder   '/'   file).default
                let command = new commandClass()

                command.run()
            }
        })
    })
})

this gives me the error:

Cannot find module './src/commands/test.js'

how do i dynamically go through all files in a folder, require/import them, and use the class function?

CodePudding user response：

You can do it with dynamic import() rather than require. Note that you'll need a package.json in src or src/commands with "type": "module" in it, since test.js uses ESM by Node.js uses CommonJS by default.

This works for me in that setup:

#! /usr/bin/env node

const fs = require("fs");
const folders = [
    "./src/commands",
    //"./my_modules/diontron/unity/src/commands",
];

folders.forEach(folder => {
    fs.readdir(folder, (err, files) => {
        files.forEach(file => {
            if (file != "index.js") {
                const modFile = folder   "/"   file;
                import(modFile)
                .then(({ default: commandClass }) => {
                    const command = new commandClass();
                    command.run();
                })
                .catch(error => {
                    console.log(`Failed to load module ${modFile}`);
                });
            }
        });
    });
});

Although that runs the code in parallel. If you want to run it in series (each waiting for the previous one to complete), you might do this (note the change from "fs" to "fs/promises" at the top):

#! /usr/bin/env node

const fs = require("fs/promises");
const folders = [
    "./src/commands",
    //"./my_modules/diontron/unity/src/commands",
];

(async () => {
    for (const folder of folders) {
        for (const folder of folders) {
            const files = await fs.readdir(folder);
            for (const file of files) {
                const { default: commandClass } = await import(folder   "/"   file);
                const command = new commandClass();
                command.run();
            }
        }
    }
})()
.catch(error => {
    console.error(error);
});

That relies on the script being run from the parent folder of the folders you're searching. If you want to use the current path instead, you should use process.cwd() to get it, then use that to resolve the folders:

#! /usr/bin/env node

const fs = require("fs");
const path = require("path"); // ***
const folders = [
    "./src/commands",
    //"./my_modules/diontron/unity/src/commands",
];

const currentDir = process.cwd(); // ***

folders.forEach(folder => {
    fs.readdir(folder, (err, files) => {
        const fullFolder = path.join(currentDir, folder); // ***
        files.forEach(file => {
            if (file != "index.js") {
                const modFile = fullFolder   "/"   file; // ***
                import(modFile)
                .then(({ default: commandClass }) => {
                    const command = new commandClass();
                    command.run();
                })
                .catch(error => {
                    console.log(`Failed to load module ${modFile}`);
                });
            }
        });
    });
});