ban-date-mutation.md

Bans mutating dates (ban-date-mutation)

Mutating dates can create confusing bugs. Instead, create new dates using a library like date-fns.

Rule Details

This rule bans methods that mutate Date.

Banned Date methods:

• setDate
• setFullYear
• setHours
• setMilliseconds
• setMinutes
• setMonth
• setSeconds
• setTime
• setUTCDate
• setUTCFullYear
• setUTCHours
• setUTCMilliseconds
• setUTCMinutes
• setUTCMonth
• setUTCSeconds
• setYear

Examples

Examples of incorrect code with the default options:

const expiration = new Date()

const noon = expiration.setHours(12)
const seventeenth = expiration.setDate(17)
const twentyTen = expiration.setFullYear(2010, 05, 23)
const thirtySeconds = expiration.setSeconds(30)

Examples of correct code with the default options:

const expiration = new Date()

import setHours from 'date-fns/setHours'
const noon = setHours(setHours, 12)

import setDate from 'date-fns/setDate'
const seventeenth = setDate(expiration, 17)

import setYear from 'date-fns/setYear'
import setMonth from 'date-fns/setMonth'
import setDate from 'date-fns/setDate'
const twentyTen = setDate(setMonth(setYear(expiration, 2010), 05), 23)

import setSeconds from 'date-fns/setSeconds'
const thirtySeconds = setSeconds(expiration, 30)

When Not To Use It

If you don't mind the risk of date mutations causing bugs in your system.