This is a fork of anton-rudeshko/node-throw. If you are familiar with the original project, see Fork Changes below.

throw2

You can't use throw statement in expressions in JavaScript:

arg = arg || throw new Error('arg is required');
//           ^^^^^
// Uncaught SyntaxError: Unexpected token 'throw'

This tiny library is wrapping throw in a function:

// Use capital T to distinguish this module from the throw keyword
const Throw = require('throw2');

// ...

arg = arg || Throw('arg is required');

This is particularly useful when using nullish coalescing operator and optional chaining operator:

value = obj?.nested?.value ?? Throw('value not found');

Installation

npm i throw2

Require/Import

CommonJS:

const Throw = require('throw2');

ESM:

import Throw from 'throw2';

More Usage Options

You can compose dynamic error messages by providing multiple arguments:

typeof arg === 'string' || Throw('Invalid arg. Received:', arg, 'Should be string.');

You can also use your own error types:

/*...expression...*/ || Throw(new MyCustomError(arg1, arg2));

// Or

/*...expression...*/ || Throw(MyCustomError, arg1, arg2); // Creates a MyCustomError with arg1 and arg2

Note

Throw as an expression is currently a Stage 2 TC39 proposal, so this package might no longer be necessary in the future.

Fork Changes

The main difference is that node-throw uses Node.js API, so it doesn't work in the browser without a polyfill. throw2 works in any CommonJS environment. (e.g. noje.js and webpack)

Also, printf-like message formatting is not supported by throw2. Use template literals instead; or pass multiple arguments to the function. (see usage examples)

License

MIT