MEPX
Chapter 7 of 16All chapters
  1. 1Introduction
  2. 2Syntax and statements
  3. 3Variables and scope
  4. 4Data types
  5. 5Comparison and coercion
  6. 6Strings
  7. 7Numbers and maths
  8. 8Arrays
  9. 9Objects
  10. 10Functions
  11. 11Conditions and loops
  12. 12Classes
  13. 13The DOM
  14. 14Events
  15. 15Promises and async
  16. 16Modules

Chapter 7 of 16

Numbers and maths

One number type, and what that costs.

Everything is a double

JavaScript has one number type, a 64 bit float, so integers and decimals share it. That is why 0.1 + 0.2 does not print as 0.3, exactly as in other languages.

  • Number.isInteger checks for a whole value, and toFixed formats for display.
  • bigint exists for integers beyond the safe range, written with a trailing n.

Converting

Number("5") and parseInt("5", 10) convert on purpose, which reads better than relying on an operator. Every arithmetic operator except plus converts to numbers, so "5" - 3 gives 2.