TypeScript:
Rounding numbers
How to:
Rounding in TypeScript can be done using several methods. Here’s a quick run-through:
// Math.round rounds to the nearest integer
console.log(Math.round(1.5)); // Output: 2
// Math.ceil rounds up to the nearest integer
console.log(Math.ceil(1.1)); // Output: 2
// Math.floor rounds down to the nearest integer
console.log(Math.floor(1.8)); // Output: 1
// toFixed rounds to a fixed number of decimal places
let num = 1.23456;
console.log(num.toFixed(2)); // Output: "1.23"
// Note: toFixed returns a string! Use parseFloat to convert back if needed.
console.log(parseFloat(num.toFixed(2))); // Output: 1.23
Deep Dive
Back in the day, rounding was a must because of limited space and precision issues in early computers. Today, floating-point arithmetic can lead to quirky results due to how numbers are stored in binary. Alternatives to rounding include floor, ceil, and trunc (for chopping off decimals without rounding).
Internals are worth noting: Math.round follows “round half up” (aka “commercial rounding”), while Math.floor and Math.ceil are straightforward. toFixed may cause unexpected results because it returns a string, and it rounds using “round half to even” (aka “bankers rounding”), especially useful to reduce bias in rounding same numbers multiple times.