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

   1 ---
   2 title: no-loss-of-precision
   3 rule_type: problem
   4 ---
   5
   6
   7
   8 This rule would disallow the use of number literals that lose precision at runtime when converted to a JS `Number` due to 64-bit floating-point rounding.
   9
  10 ## Rule Details
  11
  12 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.
  13
  14 Examples of **incorrect** code for this rule:
  15
  16 ::: incorrect
  17
  18 ```js
  19 /*eslint no-loss-of-precision: "error"*/
  20
  21 const x = 9007199254740993
  22 const x = 5123000000000000000000000000001
  23 const x = 1230000000000000000000000.0
  24 const x = .1230000000000000000000000
  25 const x = 0X20000000000001
  26 const x = 0X2_000000000_0001;
  27 ```
  28
  29 :::
  30
  31 Examples of **correct** code for this rule:
  32
  33 ::: correct
  34
  35 ```js
  36 /*eslint no-loss-of-precision: "error"*/
  37
  38 const x = 12345
  39 const x = 123.456
  40 const x = 123e34
  41 const x = 12300000000000000000000000
  42 const x = 0x1FFFFFFFFFFFFF
  43 const x = 9007199254740991
  44 const x = 9007_1992547409_91
  45 ```
  46
  47 :::