Coding Standard

• Syntax
  • Order your methods with lifecycle first and render last.
  • Name handlers handleEventName.
  • Name handlers in props onEventName.
  • Open elements on the same line.
  • Align and sort HTML properties.
  • Only export a single react class.
• Language features
  • Make "presentation" components pure.
  • Prefer props to state.
  • Use propTypes.
  • Never store state in the DOM.

Syntax

Order your methods with lifecycle first and render last.

Within your react component, you should order your methods like so:

1. lifecycle methods (in chronological order: getDefaultProps, getInitialState, componentWillMount, componentDidMount, componentWillReceiveProps, shouldComponentUpdate, componentWillUpdate, componentDidUpdate, componentWillUnmount)
2. everything else
3. render

Name handlers handleEventName.

Example:

<Component onClick={this.handleClick} onLaunchMissiles={this.handleLaunchMissiles} />

Name handlers in props onEventName.

This is consistent with React's event naming: onClick, onDrag, onChange, etc.

Example:

<Component onLaunchMissiles={this.handleLaunchMissiles} />

Open multiline elements inside parentheses

Elements that span more than 80 characters or contain multiple nodes should open on a separate line.

Yes:

return (
    <div>
        <div>
            ...
        </div>
    </div>
);

Yes:

return <div>...</div>;

No:

return <div>      // "div" is on the same line as "return"
    <div>
        ...
    </div>
</div>;

Align and sort HTML properties.

Fit them all on the same line if you can. If you can't, put each property on a line of its own, indented four spaces, in sorted order. The closing angle brace should be on a line of its own, indented the same as the opening angle brace. This makes it easy to see the props at a glance.

Yes:

<div className="highlight" key="highlight-div">
<div
    className="highlight"
    key="highlight-div"
>
<Image
    className="highlight"
    key="highlight-div"
/>

No:

<div className="highlight"      // property not on its own line
     key="highlight-div"
>
<div                            // closing brace not on its own line
    className="highlight"
    key="highlight-div">
<div                            // property is not sorted
    key="highlight-div"
    className="highlight"
>

Only export a single react class.

Every .jsx file should export a single react class, and nothing else. This is for testability: the fixture framework requires it to function.

Note the file can still define multiple classes, it just can't export more than one.

---

Language features

Make "presentation" components pure.

It's useful to think of the React world as divided into "logic" components and "presentation" components.

"Logic" components have application logic, but do not emit HTML themselves.

"Presentation" components are typically reusable, and do emit HTML.

Logic components can have internal state, but presentation components never should.

Prefer props to state.

You almost always want to use props. By avoiding state when possible, you minimize redundancy, making it easier to reason about your application.

A common pattern -- which matches the "logic" vs. "presentation" component distinction -- is to create several stateless components that just render data, and have a stateful component above them in the hierarchy that passes its state to its children via props. The stateful component encapsulates all of the interaction logic, while the stateless components take care of rendering data in a declarative way.

Copying data from props to state ​can cause the UI to get out of sync and is especially bad.

Use propTypes.

React Components should always have complete propTypes. Every attribute of this.props should have a corresponding entry in propTypes. This documents that props need to be passed to a model.

If you as passing data through to a child component, you can use the prop-type <child-class>.propTypes.<prop-name>.

Avoid these non-descriptive prop-types:

• React.PropTypes.any
• React.PropTypes.array
• React.PropTypes.object

Instead, use

• React.PropTypes.arrayOf
• React.PropTypes.objectOf
• React.PropTypes.instanceOf
• React.PropTypes.shape

As an exception, if passing data through to a child component, and you can't use <child-class>.propTypes.<prop-name> for some reason, you can use React.PropType.any.

Never store state in the DOM.

Do not use data- attributes or classes. All information should be stored in Javascript.