Adapter/JavaScript/8-promisify.js at master · HowProgrammingWorks/Adapter · GitHub

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'use strict';

const promisify = (fn) => (...args) => {

const promise = new Promise((resolve, reject) => {

const callback = (err, data) => {

if (err) reject(err);

else resolve(data);

};

fn(...args, callback);

});

return promise;

};

// Usage

const fs = require('node:fs');

const read = promisify(fs.readFile);

const main = async () => {

const fileName = '8-promisify.js';

const data = await read(fileName, 'utf8');

console.log(`File "${fileName}" size: ${data.length}`);

// Call from try/catch block

try {

const data = await read('unknown.file', 'utf8');

console.log(`File size: ${data.length}`);

} catch (error) {

console.error(error.message);

}

// Set default value in promise.catch block

const content = await read('unknown.file').catch((error) => {

console.error(error.message);

return null;

});

// Warning: note that you need additional if-statement

if (content) {

console.log({ content });

console.log(`File size: ${content.size}`);

}

};

main();

Adapter/JavaScript/8-promisify.js at master · HowProgrammingWorks/Adapter · GitHub

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