Page 72 - JavaScript

Rounding

Math.round() will round the value to the closest integer using half round up to break ties.

var a = Math.round(2.3); // a is now 2
var b = Math.round(2.7); // b is now 3
var c = Math.round(2.5); // c is now 3

But

var c = Math.round(-2.7); // c is now -3
var c = Math.round(-2.5); // c is now -2

Note how -2.5 is rounded to -2. This is because half-way values are always rounded up, that is
they're rounded to the integer with the next higher value.

Rounding up

Math.ceil() will round the value up.

var a = Math.ceil(2.3); // a is now 3
var b = Math.ceil(2.7); // b is now 3

ceiling a negative number will round towards zero

var c = Math.ceil(-1.1); // c is now 1

Rounding down

Math.floor() will round the value down.

var a = Math.floor(2.3); // a is now 2
var b = Math.floor(2.7); // b is now 2

flooring a negative number will round it away from zero.

var c = Math.floor(-1.1); // c is now -1

Truncating

Caveat: using bitwise operators (except >>>) only applies to numbers between -2147483649 and
2147483648.

2.3 | 0; // 2 (floor)
-2.3 | 0; // -2 (ceil)

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