Precision

Rounding numerical values.

In-built

Useful in-built JS functions for rounding numbers

Run
// Round up or down
Math.ceil(2.5);   // 3
Math.floor(2.5);  // 2

// Round to closest integer
Math.round(2.5);  // 3

When converting a number to a string (for printing out, for example) you can also round:

Run
// Print Pi to 2 digits
Math.PI.toFixed(2); // "3.14"

A cheeky way of rounding to a desired number of digits is by converting to a string and then back again:

Run
let p = Number.parseFloat(Math.PI.toFixed(2)); // 3.14

Decimal places

ixfx has Numbers.round

Run
import { round } from 'https://unpkg.com/ixfx/dist/numbers.js';

// Round Pi to 2 decimal places
round(2, Math.PI); // 3.14

// Make a reusable function that rounds to 2 decimal places
const r = round(2);
r(Math.PI); // 3.14

Quantise

Quantising rounds a number to a given step size. Numbers.quantiseEvery

Run
import { quantiseEvery } from 'https://unpkg.com/ixfx/dist/numbers.js';

// Round numbers to nearest multiple of 10
quantiseEvery(11, 10); // 10
quantiseEvery(25, 10); // 30

// Round to nearest decimal with 0.1
quantiseEvery(1.123, 0.1); // 1.1
quantiseEvery(1.19, 0.1);  // 1.2