no-loss-of-precision

Disallow literal numbers that lose precision

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.

Rule Details

In JS, Numbers are stored as double-precision floating-point numbers according to the IEEE 754 standard. 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.

Examples of incorrect code for this rule:

/*eslint no-loss-of-precision: "error"*/

const x = 9007199254740993
const x = 5123000000000000000000000000001
const x = 1230000000000000000000000.0
const x = .1230000000000000000000000
const x = 0X20000000000001
const x = 0X2_000000000_0001;

Examples of correct code for this rule:

/*eslint no-loss-of-precision: "error"*/

const x = 12345
const x = 123.456
const x = 123e34
const x = 12300000000000000000000000
const x = 0x1FFFFFFFFFFFFF
const x = 9007199254740991
const x = 9007_1992547409_91

Version

This rule was introduced in ESLint v7.1.0.

Resources

• Rule source
• Tests source