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

   1 ---
   2 title: no-loss-of-precision
   3 layout: doc
   4 rule_type: problem
   5 ---
   6
   7
   8
   9 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.
  10
  11 ## Rule Details
  12
  13 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.
  14
  15 Examples of **incorrect** code for this rule:
  16
  17 ::: incorrect
  18
  19 ```js
  20 /*eslint no-loss-of-precision: "error"*/
  21
  22 const x = 9007199254740993
  23 const x = 5123000000000000000000000000001
  24 const x = 1230000000000000000000000.0
  25 const x = .1230000000000000000000000
  26 const x = 0X20000000000001
  27 const x = 0X2_000000000_0001;
  28 ```
  29
  30 :::
  31
  32 Examples of **correct** code for this rule:
  33
  34 ::: correct
  35
  36 ```js
  37 /*eslint no-loss-of-precision: "error"*/
  38
  39 const x = 12345
  40 const x = 123.456
  41 const x = 123e34
  42 const x = 12300000000000000000000000
  43 const x = 0x1FFFFFFFFFFFFF
  44 const x = 9007199254740991
  45 const x = 9007_1992547409_91
  46 ```
  47
  48 :::