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Invariant

Throw descriptive error in development, generic error in production.

API

Motivation​

This package provides a simple way to throw error from an assertion and a message. It is built to be easily parsed / minified at compile time.

Usage​

import { invariant } from '@w5s/error';

function program() {
  invariant(true, 'This will not throw an error'); 
  // -> nothing
  invariant(false, 'This will throw an error'); 
  // -> throw InvariantError { message: 'Input should not be null' } when input is null or undefined

  //... do something with input
}

Coding Guide​

warning

Use invariant with caution​

In general, throwing errors is discouraged, instead Result should be used.

See explanation

invariant(
  condition, 
  // ✓ Describe what is wrong
  // ✓ Add a hint on how to fix it
  // ✓ Starts with upper case character
  // ex: '"A" is not a valid integer', 'Unexpected parameter "foo_bar"', ...
  '{{Invariant message}}'
);

FAQ​