Node.js ☛ module system



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EcmaScript module system

Node.js ☛ module system here… is CommonJS, but EcmaScript modules are preferably used from ver. 17.x. because EcmaScript module system supports asynchronous importation.

EcmaScript module system may be used by setting package.json as follows: 

 "type": "module",

Globals like __dirname or __filename are not accessible within EcmaScript module system. 

import {fileURLToPath} from "node:url";
import path from "node:path";

// import Image_processing from './Sharp'; // Compilation
import Image_processing from './Sharp.js'; // Execution

(function Main() {
    console.clear();
    // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/import.meta
    // '__filename' *IS NOT* defined in EcmaScript module scope:
    const __filename = fileURLToPath(import.meta.url); // Required: '"module": "ES2020",'
    console.info("Executable file: " + __filename + "\n");
    // '__dirname' *IS NOT* defined in EcmaScript module scope:
    const __dirname = path.dirname(fileURLToPath(import.meta.url));

    // Location of picture:
    Image_processing(path.resolve(__dirname, '..'));
})();

node:assert here… and Sharp image processing here… libraries 

import {strict as assert} from 'node:assert';
// import * as Sharp from "sharp"; // It does not work...
import Sharp from "sharp"; // '"allowSyntheticDefaultImports": true,' is required...

const Image_processing = (image_location: string) => {
    try {
        const image = Sharp(image_location + "/Lips.png");
        image.metadata().then(metadata => {
            assert.strictEqual(metadata.format, "png");
            console.log(metadata);
        });
        image.grayscale()
            .rotate(180, {background: {r: 0, g: 0, b: 0, alpha: 0}})
            .toFile("Lips_.png");
    } catch (error: unknown) {
        console.log(`An error occurred during processing: ${error}`);
    }
}

export default Image_processing;