Numbers

In modern JavaScript, there are two types of numbers:

Regular numbers in JavaScript are stored in 64\-bit format IEEE\-754, also known as “double precision floating point numbers”\. These are numbers that we’re using most of the time, and we’ll talk about them in this chapter\.

BigInt numbers represent integers of arbitrary length\. They are sometimes needed because a regular integer number can’t safely exceed \(253\-1\) or be less than \-\(253\-1\), as we mentioned earlier in the chapter Data types\. As bigints are used in a few special areas, we devote them to a special chapter BigInt\.

So here we’ll talk about regular numbers\. Let’s expand our knowledge of them\.

summary

To write numbers with many zeroes

Append "e" with the zeroes count to the number\. Like: 123e6 is the same as 123 with 6 zeroes 123000000\.A negative number after "e" causes the number to be divided by 1 with given zeroes\. E\.g\. 123e\-6 means 0\.000123 \(123 millionths\)\.

For different numeral systems:

Can write numbers directly in hex \(0x\), octal \(0o\) and binary \(0b\) systems\.parseInt\(str, base\) parses the string str into an integer in numeral system with given base, 2 ≤ base ≤ 36\.num\.toString\(base\) converts a number to a string in the numeral system with the given base\.

For regular number tests:

isNaN\(value\) converts its argument to a number and then tests it for being NaNNumber\.isNaN\(value\) checks whether its argument belongs to the number type, and if so, tests it for being NaNisFinite\(value\) converts its argument to a number and then tests it for not being NaN/Infinity/\-InfinityNumber\.isFinite\(value\) checks whether its argument belongs to the number type, and if so, tests it for not being NaN/Infinity/\-Infinity

For converting values like 12pt and 100px to a number:

Use parseInt/parseFloat for the “soft” conversion, which reads a number from a string and then returns the value they could read before the error\.

For fractions:

Round using Math\.floor, Math\.ceil, Math\.trunc, Math\.round or num\.toFixed\(precision\)\.Make sure to remember there’s a loss of precision when working with fractions\.

More mathematical functions:

See the Math object when you need them\. The library is very small but can cover basic needs\.