Javascript

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How To

Make a dynamic chain of promises

// To convert
const arr = [d1, d2, d3, ..., dn];
const fn = async (d) => { /* returns a promise */ };
// into
Promise.resolve().then(() => fn(d1)).then(() => fn(d2)).then(() => fn(d3))...then(() => fn(dn)).catch(error)
// use
arr.reduce((c, d) => c.then(() => fn(d)), Promise.resolve()).catch(error);
// OR
for (const d of arr) await fn(d);

Convert string to num shorthand

const numStr = "1.23";
const numVal = +numStr; // 1.23

Get integer part of a fraction (like Math.floor)

const fraction = 1.234;
const intPart = ~~fraction; // 1
const intPart2 = fraction << 0; // 1

The ~ operator is 2’s complement

Get an input from stdin

import * as readline from "node:readline/promises";
import { stdin as input, stdout as output } from "node:process";

const rl = readline.createInterface({ input, output });
const answer = await rl.question("What do you think of Node.js? ");
console.log(`Thank you for your valuable feedback: ${answer}`);
rl.close();