Disallow Magic Numbers (no-magic-numbers)

‘Magic numbers’ are numbers that occur multiple time in code without an explicit meaning. They should preferably be replaced by named constants.

var now = Date.now(),
    inOneHour = now + (60 * 60 * 1000);

Rule Details

The no-magic-numbers rule aims to make code more readable and refactoring easier by ensuring that special numbers are declared as constants to make their meaning explicit.

The following pattern is considered a problem:

/*eslint no-magic-numbers: 2*/

var dutyFreePrice = 100,
    finalPrice = dutyFreePrice + (dutyFreePrice * 0.25); /*error No magic number: 0.25*/

The following pattern is considered okay:

/*eslint no-magic-numbers: 2*/

var TAX_PERCENTAGE = 0.25;

var dutyFreePrice = 100,
    finalPrice = dutyFreePrice + (dutyFreePrice * TAX_PERCENTAGE);

Options

ignore

An array of numbers to ignore. It’s set to [0, 1, 2] by default. If provided, it must be an Array.

enforceConst

A boolean to specify if we should check for the const keyword in variable declaration of numbers. false by default.

detectObjects

A boolean to specify if we should detect numbers when setting object properties for example. false by default.

Version

This rule was introduced in ESLint 1.7.0.