Function isNumber

Example

Basic usage

isNumber(0) // true
isNumber(1) // true
isNumber(2.2) // true
isNumber(NaN) // true
isNumber(Infinity) // true

isNumber('3') // false
isNumber(null) // false
Copy

Type narrowing

const value: number | string

if (isNumber(value)) {
  value // type: number
} else {
  value // type: string
}

// or
if (!isNumber(value)) {
  value // type: string
} else {
  value // type: number
}
Copy

Paired with assert

import { assert } from 'uft'

const paid: number | null
assert(isNumber(paid), 'missing payment')
paid // type: number
Copy