JavaScript — Math

The Math namespace

No instantiation — just call it:

Math.PI;      // 3.141592653589793
Math.E;       // 2.718…
Math.SQRT2;

Rounding — four flavors

Call	4.5	-4.5	Meaning
Math.round	5	-4	nearest
Math.floor	4	-5	always down
Math.ceil	5	-4	always up
Math.trunc	4	-4	chop decimals

Negative-number differences between floor/trunc are a classic quiz trap.

Powers, roots, absolutes

Math.pow(2, 8);   // 256   (or 2 ** 8)
Math.sqrt(81);    // 9
Math.cbrt(27);    // 3
Math.abs(-10);    // 10
Math.sign(-7);    // -1 · 1 · 0 by sign
Math.hypot(3, 4); // 5    √(a²+b²)

Min / max (with spread for arrays)

Math.max(10, 20, 5);        // 20
const nums = [10, 30, 5];
Math.max(...nums);          // 30

Random recap

Math.random();                              // [0, 1)
function randInt(min, max) {                // inclusive both ends
    return Math.floor(Math.random() * (max - min + 1)) + min;
}
randInt(1, 10);

Security: Math.random() is predictable. Tokens/passwords need crypto.getRandomValues().

Trig & logs

Math.sin(Math.PI / 2);   // 1     radians only!
const rad = deg => deg * Math.PI / 180;
Math.log10(100);         // 2
Math.log2(8);            // 3
Math.exp(1);             // e

Floating-point reminder

0.1 + 0.2;               // 0.30000000000000004
(12.3456).toFixed(2);    // "12.35" — STRING result!

Round before comparing; format at display.

Mini Practice

1. Table of round/floor/ceil/trunc across positives and negatives.
2. Array max/min via spread.
3. randInt dice simulator; tally 600 rolls.
4. deg↔rad converters; verify sin(90°)=1.
5. Hypotenuse calculator.
6. Demonstrate the 0.1+0.2 artifact and its toFixed fix.

Next: break →