Code Reference

Math

JavaScript · Reference cheat sheet

Math

JavaScript · Reference cheat sheet

📋 Overview

Math is a built-in object of numeric constants and functions. It works on IEEE-754 numbers (not BigInt). Prefer Math helpers over hand-rolled formulas for clamping, rounding, and trig.

🔧 Core concepts

  • Constants: Math.PI, Math.E, Math.LN2, Math.SQRT2, …
  • Rounding: floor, ceil, round, trunc, fround.
  • Min/max: Math.min(...), Math.max(...) — watch empty call → Infinity / -Infinity.
  • Random: Math.random() ∈ [0, 1).
  • Powers: sqrt, cbrt, pow, ** operator, hypot, abs, sign.
  • Trig: sin, cos, tan, atan2 (radians).
Math.clamp?.(0, 5, 10); // if available; else DIY
const clamp = (n, min, max) => Math.min(max, Math.max(min, n));

💡 Examples

const clamp = (n, min, max) => Math.min(max, Math.max(min, n));
clamp(120, 0, 100); // 100

Math.trunc(3.9); // 3
Math.floor(-3.1); // -4
Math.trunc(-3.1); // -3

// Inclusive integer random
function randomInt(min, max) {
  return Math.floor(Math.random() * (max - min + 1)) + min;
}

// Sum with hypot for distance
const dist = Math.hypot(dx, dy);

// Percentage
const pct = Math.round((done / total) * 100);

// Avoid float noise for currency — use integers (cents) or Decimal libs
const cents = Math.round(19.99 * 100); // 1999

// Spread min/max on arrays
const nums = [3, 1, 4];
Math.max(...nums); // 4
// Large arrays: use loop or reduce to avoid stack limits
nums.reduce((a, b) => Math.max(a, b), -Infinity);
// Angle helpers
const toRad = (deg) => (deg * Math.PI) / 180;
const toDeg = (rad) => (rad * 180) / Math.PI;
Math.sin(toRad(90)); // ~1

// imul / clz32 for bit ops
Math.imul(0xffffffff, 2);

// Sign & absolute
Math.sign(-0); // -0
Math.abs(-4.2); // 4.2
Math.log2(8); // 3

⚠️ Pitfalls

  • Math.max() with no args is -Infinity; Math.min() is Infinity.
  • Math.round uses “round half away from zero” toward +∞ for .5 on positives.
  • Floating point: 0.1 + 0.2 !== 0.3 — compare with epsilon.
  • Math.random is not cryptographically secure — use crypto.getRandomValues.
  • Spreading huge arrays into Math.max can throw RangeError.

🔗 Related

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Math📋 Overview🔧 Core concepts💡 Examples⚠️ Pitfalls🔗 Related