Math Object

Math Object

What it means

The built-in Math object provides constants and static methods for numeric operations — rounding, trigonometry, random numbers, min/max, and more. Unlike most JS objects, you never instantiate Math — you call its methods directly, e.g. Math.round(), not new Math().

Examples

console.log(Math.round(4.5));    // 5
console.log(Math.floor(4.9));    // 4
console.log(Math.ceil(4.1));     // 5
console.log(Math.abs(-7));       // 7
console.log(Math.max(3, 7, 2));  // 7
console.log(Math.min(3, 7, 2));  // 2
console.log(Math.pow(2, 10));    // 1024 (also: 2 ** 10)
console.log(Math.sqrt(16));      // 4

// Random integer between min and max (inclusive)
function randomInt(min, max) {
  return Math.floor(Math.random() * (max - min + 1)) + min;
}
console.log(randomInt(1, 6));    // simulates a dice roll

Common mistake

Assuming Math.random() includes the upper bound, or forgetting Math.floor() when generating a random integer — Math.random() returns a float in [0, 1), so without flooring you get a float, and without the +1 adjustment your range excludes the max value.

// Bug: returns a float, not an integer, and never quite reaches `max`
function randomInt(min, max) {
  return Math.random() * (max - min) + min;
}

// Correct: floors to an integer and includes both min and max
function randomInt(min, max) {
  return Math.floor(Math.random() * (max - min + 1)) + min;
}

Quick practice

1. What range of values does Math.random() return?

   Answer

   A float from 0 (inclusive) up to but not including 1 — [0, 1).

2. What’s the difference between Math.floor() and Math.round() for 4.5?

   Answer

   Math.floor(4.5) gives 4 (always rounds down); Math.round(4.5) gives 5 (rounds to the nearest integer, halves round up).

3. How do you generate a random integer between 1 and 6 (inclusive), like a dice roll?

   Answer

   Math.floor(Math.random() * 6) + 1