roundToStep function

Rounds a number to the nearest multiple of a step, without float noise: roundToStep(0.3, 0.1) is 0.3.

import { roundToStep } from 'utils';

Signature

export function roundToStep(value: number, step = 1): number

Parameters

Name	Description
value	The number to round.
step	The step, a positive number such as 0.1, 0.25 or 5. Defaults to 1.

Returns

The nearest multiple of step, with no more decimals than step.

Example

roundToStep(0.29, 0.1); // 0.3
roundToStep(8, 5); // 10

Tests

Line coverage: 100 %.

• ✅ rounds 0.3 to step 0.1 as 0.3
• ✅ rounds 0.29 to step 0.1 as 0.3
• ✅ rounds 7 to step 5 as 5
• ✅ rounds 8 to step 5 as 10
• ✅ rounds -7 to step 5 as -5
• ✅ rounds 1.23456 to step 0.25 as 1.25
• ✅ rounds 3.7e-7 to step 1e-7 as 4e-7
• ✅ rounds 0.7 to step 0.1 as 0.7
• ✅ rounds 0.44 to step 0.30000000000000004 as 0.3
• ✅ rounds 1.23456 to step 1e-100 as 1.23456
• ✅ takes the defaults

Source

src/math/round-to-step.ts (on GitHub)

Files it needs

src/math/round-to-step.ts imports, directly or not:

• src/math/internal/snap-to-step.ts
• src/math/round-to-fraction-digits.ts

Source code

import { snapToStep } from './internal';

/**
 * Rounds a number to the nearest multiple of a step, without float noise: `roundToStep(0.3, 0.1)` is `0.3`.
 *
 * @param value - The number to round.
 * @param step - The step, a positive number such as `0.1`, `0.25` or `5`. Defaults to `1`.
 * @returns The nearest multiple of `step`, with no more decimals than `step`.
 * @example
 * roundToStep(0.29, 0.1); // 0.3
 * roundToStep(8, 5); // 10
 */
export function roundToStep(value: number, step = 1): number {
  return snapToStep(value, step, Math.round);
}

Test file

import { roundToStep } from './round-to-step';

describe(roundToStep, () => {
  it.for([
    [0.3, 0.1, 0.3],
    [0.29, 0.1, 0.3],
    [7, 5, 5],
    [8, 5, 10],
    [-7, 5, -5],
    [1.23456, 0.25, 1.25],
    [0.00000037, 1e-7, 0.0000004],
    [0.7, 0.1, 0.7],
    [0.44, 0.1 + 0.2, 0.3],
    [1.23456, 1e-100, 1.23456],
  ] as const)('rounds %s to step %s as %s', ([value, step, expected]) => {
    expect(roundToStep(value, step)).toBe(expected);
  });

  it('takes the defaults', () => {
    expect(roundToStep(2.5)).toStrictEqual(roundToStep(2.5, 1));
  });
});

Keywords: round, to, step, math, function