if-else-throw

If X, return Y, else throw Z.
X can be a boolean or a function.

Installation

Requires Node.js 6.0.0 or above.

npm i if-else-throw

API

The module exports a single function.

Parameters

1. test (any): The “if” condition, evaluated for truthiness. If a function is provided, it is called with val as its only argument and its return value is used.
2. Optional: val (any): The “then” value to return if test is truthy. If omitted, test is returned.
3. Optional: error (Error or string): The Error to throw if test is falsely. If a string is provided, it is wrapped in a new Error. If omitted, defaults to new Error().

Return Value

If test is truthy, returns val (or returns test if val is omitted). If test is falsey, there is no return value because an error is thrown.

Examples

const ifElseThrow = require('if-else-throw')

const value = []
ifElseThrow(
  Array.isArray(value), // The boolean condition (in this case, true)
  value, // The value returned if true
  new TypeError('Not an array') // The error thrown if false
) // []

ifElseThrow(
  x => Array.isArray(x), // x will be the second argument ('this is a string')
  'this is a string', // Given to the function and returned if the function returns true
  new TypeError('Not an array') // The error thrown if false
) // Uncaught TypeError: Not an array

ifElseThrow(
  'this is truthy',
  'Must be truthy'
) // 'this is truthy'

ifElseThrow(
  null,
  'Must be truthy'
) // Uncaught Error: Must be truthy