1
In some cultures, periods are used as thousands separators, and commas are used as the decimal separator,
opposite from what you may be used to.
CHAPTER 16
Math
This chapter describes JavaScript’s built-in
Math
object, which contains math func‐
tions commonly encountered in application development (if you are doing sophisti‐
cated numeric analysis, you may have to find third-party libraries).
Before we delve into the library, let’s remind ourselves how JavaScript handles num‐
bers. In particular, there’s no dedicated integer class; all numbers are IEEE 754 64-bit
floating-point numbers. For most functions in the math library, this simplifies things:
a number is a number. While no computer will ever be able to fully represent an arbi‐
trary real number, for practical purposes, you can think of JavaScript numbers as real
numbers. Note that there’s no built-in support for complex numbers in JavaScript. If
you need complex numbers, bignums, or more sophisticated structures or algorithms,
Outside of some basics, this chapter is not designed to teach you math; that’s a book
(or 2 or 10) of its own.
Throughout the code comments in this chapter, I will use a tilde (~) prefix to indicate
that a given value is approximate. I will also refer to properties of the
Math
object as
functions, not methods. While they are technically static methods, the distinction is
academic here, as the
Math
object provides namespacing, not context.
Formatting Numbers
A common need is to format numbers; that is, instead of displaying 2.0093, you want
to display 2.1. Or instead of displaying 1949032, you want to display 1,949,032.
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