Function isDefined

Example

Basic usage

isDefined({}) // true
isDefined(false) // true
isDefined(null) // true
isDefined(undefined) // false
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Type narrowing

const value: { foo: string } | undefined

if (isDefined(value)) {
  value // type: { foo: string }
} else {
  value // type: undefined
}

// or
if (!isDefined(value)) {
  value // type: undefined
} else {
  value // type: { foo: string }
}
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Paired with assert

import { assert } from 'uft'

const token: string | undefined
assert(isDefined(token), 'token is not defined')
token // type: string
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