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Nullish Coalescing Operator (??)
by Mac WasilewskiJanuary 23rd, 2022
Too Long; Didn't Read
Nullish coalescing operator (??) instead of a logical or (?) is a safer operator. The OR operator will check for `falsy`. The **nullish coalesce** operator on the other hand tests for `null` and ‘undefined` only. The main purpose is to simplify assigning default values. We don’t want Javascript to do with it anything else, just return the data.
If you use @typescript-eslint you might see this error:
Prefer using nullish coalescing operator (??) instead of a logical or (||), as it is a safer operator.
Why??????
Nullish coalescing operator
Nullish coalescing is an improvement added to Typescript a while ago and officially added to 2020 Javascript. The main purpose is to simplify assigning default values.
Let’s jump to the code:
// Nullish coalescing
console.log(0 ?? 'error') // 0
console.log('' ?? 'error') // ''
console.log(null ?? 'error') // 'error'
Nothing special? Have a look at how ‘OR’ would behave
// 'good-old' OR operator
console.log(0 || 'error') // 'error'
console.log('' || 'error') // 'error'
console.log(null || 'error') // 'error'
See the difference? The OR operator will check for falsy and for Javascript 0 and ’’ are considered false in a boolean context.
See what evaluates to false here.
The nullish coalescing operator on the other hand tests for null and undefined only.
Returning an ’’ or 0 might be what we want. We don’t want Javascript to do with it anything else, just return the data!
L O A D I N G
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