You can format currency to 2 decimals in TypeScript with Intl.NumberFormat: pass style: ‘currency’ and currency: ‘USD’, and you get a string like $1,234.50 with the symbol, commas and two decimals: Every output on this page came from a real run with TypeScript 7.0.2 and Node.js v22.22.2, strict mode on. Format currency to 2 decimals … Read more >>
The quickest way to convert number to boolean in TypeScript is Boolean(n) or !!n. Both return false for 0, -0 and NaN, and true for every other number, including negatives and Infinity: I ran each snippet below with TypeScript 7.0.2 and Node.js v22.22.2 in strict mode, so the console output you see is real. We’ll … Read more >>
The require keyword in TypeScript is really Node.js’s CommonJS require() function: it loads a module synchronously and returns its exports. In a .ts file it needs Node’s types, and it returns any, so prefer import x = require() or plain import: Every example here ran on TypeScript 7.0.2 and Node.js v22.22.2, compiled in strict mode. … Read more >>
You can get the decimal part of a number in TypeScript with the remainder operator: x % 1 returns everything after the decimal point as a number. For 24.75 that’s 0.75, and an integer gives 0: My test machine runs TypeScript 7.0.2 and Node.js v22.22.2; I built each file with strict checks on and copied … Read more >>
To find a key by value in a TypeScript dictionary, get the keys with Object.keys(), type them as keyof, and call find() to return the first key whose value matches. If nothing matches, you get undefined: Nothing below is pseudo-code: each lookup went through tsc –strict and then Node, using TypeScript 7.0.2 and Node.js v22.22.2, … Read more >>
ReferenceError: fetch is not defined in TypeScript means your compiled JavaScript is running somewhere that has no global fetch, usually Node.js older than 18 or a Jest jsdom test. Upgrade Node, or load node-fetch first: Every example below ran on TypeScript 7.0.2 and Node.js v22.22.2 with strict mode, and I copied the output straight from … Read more >>
The default keyword in TypeScript has two jobs. export default marks the main value a module exports, and default: in a switch runs when no case matches. Here are both in two lines: Every snippet below was compiled in strict mode with TypeScript 7.0.2 and Node.js v22.22.2; the output comes straight from those runs. You’ll … Read more >>
To get the first element from a TypeScript dictionary, read index 0 of Object.entries() for a plain object or Record, and call .entries().next().value for a Map. Both give back undefined when the dictionary is empty: I ran all five examples with TypeScript 7.0.2 and Node.js v22.22.2 (strict mode on), so the outputs you see are … Read more >>
TypeScript keyof string confusion has one cause: keyof T isn’t always a string. In a generic it’s string | number | symbol, so narrow it with keyof T & string, and turn a runtime string into a key with a type guard: My test setup was TypeScript 7.0.2 and Node.js v22.22.2 with –strict on. Each … Read more >>
The quickest way to round to 2 decimals in TypeScript is Math.round(value * 100) / 100, which returns a number. It breaks on halfway values like 1.005, though, so when every cent matters, shift the decimal point with exponent notation instead: I ran every snippet through TypeScript 7.0.2 and Node.js v22.22.2 in strict mode, so … Read more >>