Motivation

Since JavaScript is a dynamic programming language with weak type system built-in, it requires much more cautious when writing and using APIs. Library such as React provides a way to force property validation using propTypes.

With the similar ideas, paramTypes will do the same trick to enhance function calls in development mode. While in production mode, the validation will be removed so that the performance won't be affected.

How to use

paramTypes.validate is the core API to call. It's a high order function that requires two steps to setup. First configure, then validate.

Here is an example:

import * as paramTypes from 'paramTypes';

// define
const validator = paramTypes.validate(
  'function name', // this will be used in error message to help locate the issue
  paramTypes.number.isRequired,
  paramTypes.restOf(paramTypes.string.isRequired),
);

function example(num, ...names) {
  validator(num, ...names);
  // do something
}

example(1, 'Anna', 'Bob', 'Claire');

paramTypes provides similar validators as propTypes in React.

Also, it provides two mode of validation.

• Use paramTypes.validate to validate parameters and output warning in console only

  The actual workflow won't be affected in this way.

• Use paramTypes.validateWithError to validate parameters and throw the first error occurs.

  The actual workflow will be interrupted in this way.

Production Mode

Do not forget to remove validation in production mode.

To do this, all you need to do is set process.env.NODE_ENV to "production".