@jrc03c/js-math-tools/src/for-each.test.mjs

some math tools for JS

import { copy } from "./copy.mjs"
import { expect, test } from "@jrc03c/fake-jest"
import { forEach } from "./for-each.mjs"
import { mean } from "./mean.mjs"
import { normal } from "./normal.mjs"
import { range } from "./range.mjs"
import { time } from "./time.mjs"

test("tests that the `forEach` function is faster than `Array.prototype.forEach`", () => {
  // NOTE: For some extremely weird reason that I don't understand, this test
  // fails when placed *after* the test below! I've confirmed that it only fails
  // (1) when run via `fake-jest` (2) when placed after the function below. It
  // does *not* fail when placed above the test below *or* when run via regular
  // Node invocation (i.e., just running this code on its own in a new script
  // (without the `expect` bit at the end)).
  const x = range(0, 1e7).map(() => Math.random())
  const fn = v => Math.sqrt(v)
  const time1 = mean(range(0, 10).map(() => time(() => x.forEach(fn))))
  const time2 = mean(range(0, 10).map(() => time(() => forEach(x, fn))))
  expect(time2).toBeLessThan(time1)
})

test("tests that the `forEach` function works as expected", () => {
  const a = normal(100)
  const b = copy(a)
  forEach(b, (v, i) => (b[i] *= 2))
  expect(a.length).toBe(100)
  expect(b.length).toBe(100)

  a.forEach((v, i) => {
    expect(b[i]).toBeCloseTo(a[i] * 2)
  })
})