eslint/docs/rules/no-loss-of-precision.md

   1 # Disallow Number Literals That Lose Precision (no-loss-of-precision)
   2
   3 This rule would disallow the use of number literals that immediately lose precision at runtime when converted to a JS `Number` due to 64-bit floating-point rounding.
   4
   5 ## Rule Details
   6
   7 In JS, `Number`s are stored as double-precision floating-point numbers according to the [IEEE 754 standard](https://en.wikipedia.org/wiki/IEEE_754). Because of this, numbers can only retain accuracy up to a certain amount of digits. If the programmer enters additional digits, those digits will be lost in the conversion to the `Number` type and will result in unexpected behavior.
   8
   9 Examples of **incorrect** code for this rule:
  10
  11 ```js
  12 /*eslint no-loss-of-precision: "error"*/
  13
  14 const x = 9007199254740993
  15 const x = 5123000000000000000000000000001
  16 const x = 1230000000000000000000000.0
  17 const x = .1230000000000000000000000
  18 const x = 0X20000000000001
  19 const x = 0X2_000000000_0001;
  20 ```
  21
  22 Examples of **correct** code for this rule:
  23
  24 ```js
  25 /*eslint no-loss-of-precision: "error"*/
  26
  27 const x = 12345
  28 const x = 123.456
  29 const x = 123e34
  30 const x = 12300000000000000000000000
  31 const x = 0x1FFFFFFFFFFFFF
  32 const x = 9007199254740991
  33 const x = 9007_1992547409_91
  34 ```