A ReactJS Mixin which enforces that a Component document all its props in propTypes.

<script src="prop-validation-mixin.js"></script>

<div id="content"></div>

<script type="text/jsx">
/** @React.DOM */

var Root = React.createComponent({
  propTypes: {
    name: React.PropTypes.string.isRequired
  },
  mixins: [PropValidationMixin],
  render: function() {
    return <div>{this.props.name}</div>;
  }
});

React.renderComponent(<Root name="Bob" />, document.getElementById('content'));
</script>

This enforces a requirement that every prop that the Root component accesses appears in propTypes (at least in dev mode on browsers which support it, see below).

It's good practice to document the API of your components. The propTypes field lets you do this in a way that's enforced at runtime and hence unlikely to drift vs. the implementation.

The built-in propTypes system is more of a property validation system than a complete API spec. There's nothing that forces you to enumerate all your component's props in the propTypes section. This Mixin changes that.

If you want to use a component and you see mixins: [PropValidationMixin], then you can be confident that its propTypes section specifies its complete API.

When you mix in PropValidationMixin, it wraps an ES6 Proxy around this.props which intercepts all reads from this.props. When you read this.props.foo, it checks that foo appears in this.propTypes. This ensures that the component can't ever use a property that it doesn't specify.

Note that this requires the ES6 Proxy, which is currently only supported in Firefox.

Just like propTypes, PropValidationMixin is a no-op when you use the production version of ReactJS (i.e. the minified version). It won't affect the performance or behavior of your site.

To get going, run:

npm install

Then open test/dev.html in Firefox.