Stateless React components

React v0.14.0 introduces “stateless” components, which takes a more functional approach to creating chunks of JSX and templates. In my previous article on creating a tab component I created the components using the traditional way, using React.createClass() or ES6 Classes that extend React.Component.

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Traditional components

Prior to v0.14.0, we would create React components using React.createClass() (or extending React.Component with ES6 Classes) and pass in an Object definition. This is great, however many components we can create are merely template boilerplate code that’s injected into another component, therefore there becomes boilerplate bloat for small reusable chunks of code.

Taking the Pane component from the previous article, let’s look how that looks.

Here we use React.createClass(), where we have a propTypes property and render property.

const Pane = React.createClass({
  propTypes: {
    label: React.PropTypes.string.isRequired,
    children: React.PropTypes.element.isRequired
  },
  render() {
    return (
      <div>
        {this.props.children}
      </div>
    );
  }
});

Here we use class Pane extends React.Component, where we no longer have a propTypes property and instead move it to a property of the class itself, using Pane.propTypes. We keep the render property.

class Pane extends React.Component {
  render() {
    return (
      <div>
        {this.props.children}
      </div>
    );
  }
}
Pane.propTypes = {
  label: React.PropTypes.string.isRequired,
  children: React.PropTypes.element.isRequired
};

This component has a displayName which isn’t a necessity, however propTypes is a nice-to-have and render is pretty essential. It’s a lot of boilerplate code for a component that simply passes this.props.children through into the new component.

Enter stateless components

With stateless components, we can kill the entire boilerplate code and keep everything (in some cases) a single line of code. Stateless functions are merely intended to return a specific template that can take dynamic properties, which could be higher level components such as lists, inputs and so on. They will not have any state Objects bound to them.

Let’s look at how we can refactor the above example to use a stateless component approach.

const Pane = (props) => <div>{props.children}</div>;

Done.

Or in ES5:

var Pane = function (props) {
  return <div>{props.children}</div>;
};

Adding in propTypes we mirror the ES6 syntax by adding a property to the Pane constant:

const Pane = (props) => <div>{props.children}</div>;
Pane.propTypes = {
  label: React.PropTypes.string.isRequired,
  children: React.PropTypes.element.isRequired
};

Note how we no longer refer to the this keyword, and the arguments of the stateless component function become the “props”.

When supplying default props (or other Object definition props) to a component, this would also be done using Pane.defaultProps.