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React

Mostly reasonable patterns for writing React on Rails

Table of Contents

1. Scope
2. Organization
3. Component Organization
4. Formatting Props
5. Patterns
6. Computed Props
7. Compound State
8. prefer-ternary-to-sub-render
9. View Components
10. Container Components
11. Anti-patterns
12. Compound Conditions
13. Cached State in render
14. Existence Checking
15. Setting State from Props
16. Practices
17. Naming Handle Methods
18. Naming Events
19. Using PropTypes
20. Using Entities
21. Gotchas
22. Tables
23. Libraries
24. classnames
25. Other
26. JSX
27. ES2015
28. react-rails
29. rails-assets
30. flux

---

Scope

This is how we write React.js on Rails. We've struggled to find the happy path. Recommendations here represent a good number of failed attempts. If something seems out of place, it probably is; let us know what you've found.

All examples written in ES2015 syntax now that the official react-rails gem ships with babel.

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---

Component Organization

• class definition
  • constructor
    • event handlers
  • 'component' lifecycle events
  • getters
  • render
• defaultProps
• proptypes

class Person extends React.Component {
  constructor (props) {
    super(props);

    this.state = { smiling: false };

    this.handleClick = () => {
      this.setState({smiling: !this.state.smiling});
    };
  }

  componentWillMount () {
    // add event listeners (Flux Store, WebSocket, document, etc.)
  }

  componentDidMount () {
    // React.getDOMNode()
  }

  componentWillUnmount () {
    // remove event listeners (Flux Store, WebSocket, document, etc.)
  }

  get smilingMessage () {
    return (this.state.smiling) ? "is smiling" : "";
  }

  render () {
    return (
      <div onClick={this.handleClick}>
        {this.props.name} {this.smilingMessage}
      </div>
    );
  }
}

Person.defaultProps = {
  name: 'Guest'
};

Person.propTypes = {
  name: React.PropTypes.string
};

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Formatting Props

Wrap props on newlines for exactly 2 or more.

// bad
<Person
 firstName="Michael" />

// good
<Person firstName="Michael" />

// bad
<Person firstName="Michael" lastName="Chan" occupation="Designer" favoriteFood="Drunken Noodles" />

// good
<Person
 firstName="Michael"
 lastName="Chan"
 occupation="Designer"
 favoriteFood="Drunken Noodles" />

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---

Computed Props

Use getters to name computed properties.

  // bad
  firstAndLastName () {
    return `${this.props.firstName} ${this.props.lastName}`;
  }

  // good
  get fullName () {
    return `${this.props.firstName} ${this.props.lastName}`;
  }

See: Cached State in render anti-pattern

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---

Compound State

Prefix compound state getters with a verb for readability.

// bad
happyAndKnowsIt () {
  return this.state.happy && this.state.knowsIt;
}

// good
get isHappyAndKnowsIt () {
  return this.state.happy && this.state.knowsIt;
}

These methods MUST return a boolean value.

See: Compound Conditions anti-pattern

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Prefer Ternary to Sub-render

Keep logic inside the render function.

// bad
renderSmilingStatement () {
  return <strong>{(this.state.isSmiling) ? " is smiling." : ""}</strong>;
},

render () {
  return <div>{this.props.name}{this.renderSmilingStatement()}</div>;
}

// good
render () {
  return (
    <div>
      {this.props.name}
      {(this.state.smiling)
        ? <span>is smiling</span>
        : null
      }
    </div>
  );
}

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View Components

Compose components into views. Don't create one-off components that merge layout and domain components.

// bad
class PeopleWrappedInBSRow extends React.Component {
  render () {
    return (
      <div className="row">
        <People people={this.state.people} />
      </div>
    );
  }
}

// good
class BSRow extends React.Component {
  render () {
    return <div className="row">{this.props.children}</div>;
  }
}

class SomeView extends React.Component {
  render () {
    return (
      <BSRow>
        <People people={this.state.people} />
      </BSRow>
    );
  }
}

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Container Components

A container does data fetching and then renders its corresponding sub-component. That's it. — Jason Bonta

Bad

// CommentList.js

class CommentList extends React.Component {
  getInitialState () {
    return { comments: [] };
  }

  componentDidMount () {
    $.ajax({
      url: "/my-comments.json",
      dataType: 'json',
      success: function(comments) {
        this.setState({comments: comments});
      }.bind(this)
    });
  }

  render () {
    return (
      <ul>
        {this.state.comments.map(({body, author}) => {
          return <li>{body}—{author}</li>;
        })}
      </ul>
    );
  }
}

Good

// CommentList.js

class CommentList extends React.Component {
  render() {
    return (
      <ul>
        {this.props.comments.map(({body, author}) => {
          return <li>{body}—{author}</li>;
        })}
      </ul>
    );
  }
}

// CommentListContainer.js

class CommentListContainer extends React.Component {
  getInitialState () {
    return { comments: [] }
  }

  componentDidMount () {
    $.ajax({
      url: "/my-comments.json",
      dataType: 'json',
      success: function(comments) {
        this.setState({comments: comments});
      }.bind(this)
    });
  }

  render () {
    return <CommentList comments={this.state.comments} />;
  }
}

Read more
Watch more

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---

Cached State in render

Do not keep state in render

// bad
render () {
  let name = `Mrs. ${this.props.name}`;

  return <div>{name}</div>;
}

// good
render () {
  return <div>{`Mrs. ${this.props.name}`}</div>;
}

// best
get fancyName () {
  return `Mrs. ${this.props.name}`;
}

render () {
  return <div>{this.fancyName}</div>;
}

This is mostly stylistic and keeps diffs nice. I doubt that there's a significant perf reason to do this.

See: Computed Props pattern

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Compound Conditions

Don't put compound conditions in render.

// bad
render () {
  return <div>{if (this.state.happy && this.state.knowsIt) { return "Clapping hands" }</div>;
}

// better
get isTotesHappy() {
  return this.state.happy && this.state.knowsIt;
},

render() {
  return <div>{(this.isTotesHappy) && "Clapping hands"}</div>;
}

The best solution for this would use a container component to manage state and pass new state down as props.

See: Compound State pattern

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Existence Checking

Do not check existence of props at the root of a component. Components should not have two possible return types.

// bad
const Person = props => {
  if (this.props.firstName)
    return <div>{this.props.firstName}</div>
  else
    return null
}

Components should always render. Consider adding defaultProps, where a sensible default is appropriate.

// better
const Person = props =>
  <div>{this.props.firstName}</div>

Person.defaultProps = {
  firstName: "Guest"
}

If a component should be conditionally rendered, handle that in the owner component.

// best
const TheOwnerComponent = props =>
  <div>
    {props.person && <Person {...props.person} />}
  </div>

This is only where objects or arrays are used. Use PropTypes.shape to clarify the types of nested data expected by the component.

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Setting State from Props

Do not set state from props without obvious intent.

// bad
getInitialState () {
  return {
    items: this.props.items
  };
}

// good
getInitialState () {
  return {
    items: this.props.initialItems
  };
}

Read: "Props in getInitialState Is an Anti-Pattern"

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---

Naming Handler Methods

Name the handler methods after their triggering event.

// bad
punchABadger () { /*...*/ },

render () {
  return <div onClick={this.punchABadger} />;
}

// good
handleClick () { /*...*/ },

render () {
  return <div onClick={this.handleClick} />;
}

Handler names should:

• begin with handle
• end with the name of the event they handle (eg, Click, Change)
• be present-tense

If you need to disambiguate handlers, add additional information between handle and the event name. For example, you can distinguish between onChange handlers: handleNameChange and handleAgeChange. When you do this, ask yourself if you should be creating a new component.

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Naming Events

Use custom event names for ownee events.

class Owner extends React.Component {
  handleDelete () {
    // handle Ownee's onDelete event
  }

  render () {
    return <Ownee onDelete={this.handleDelete} />;
  }
}

class Ownee extends React.Component {
  render () {
    return <div onChange={this.props.onDelete} />;
  }
}

Ownee.propTypes = {
  onDelete: React.PropTypes.func.isRequired
};

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Using PropTypes

Use PropTypes to communicate expectations and log meaningful warnings.

MyValidatedComponent.propTypes = {
  name: React.PropTypes.string
};

MyValidatedComponent will log a warning if it receives name of a type other than string.

<Person name=1337 />
// Warning: Invalid prop `name` of type `number` supplied to `MyValidatedComponent`, expected `string`.

Components may also require props.

MyValidatedComponent.propTypes = {
  name: React.PropTypes.string.isRequired
}

This component will now validate the presence of name.

<Person />
// Warning: Required prop `name` was not specified in `Person`

Read: Prop Validation

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Using Entities

Use React's String.fromCharCode() for special characters.

// bad
<div>PiCO · Mascot</div>

// nope
<div>PiCO &middot; Mascot</div>

// good
<div>{'PiCO ' + String.fromCharCode(183) + ' Mascot'}</div>

// better
<div>{`PiCO ${String.fromCharCode(183)} Mascot`}</div>

Read: JSX Gotchas

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Tables

The browser thinks you're dumb. But React doesn't. Always use tbody in table components.

// bad
render () {
  return (
    <table>
      <tr>...</tr>
    </table>
  );
}

// good
render () {
  return (
    <table>
      <tbody>
        <tr>...</tr>
      </tbody>
    </table>
  );
}

The browser is going to insert tbody if you forget. React will continue to insert new trs into the table and confuse the heck out of you. Always use tbody.

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classnames

Use classNames to manage conditional classes.

// bad
get classes () {
  let classes = ['MyComponent'];

  if (this.state.active) {
    classes.push('MyComponent--active');
  }

  return classes.join(' ');
}

render () {
  return <div className={this.classes} />;
}

// good
render () {
  let classes = {
    'MyComponent': true,
    'MyComponent--active': this.state.active
  };

  return <div className={classnames(classes)} />;
}

Read: Class Name Manipulation

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JSX

We used to have some hardcore CoffeeScript lovers is the group. The unfortunate thing about writing templates in CoffeeScript is that it leaves you on the hook when certain implementations changes that JSX would normally abstract.

We no longer recommend using CoffeeScript to write render.

For posterity, you can read about how we used CoffeeScript, when using CoffeeScript was non-negotiable: CoffeeScript and JSX.

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ES2015

react-rails now ships with babel. Anything you can do in Babel, you can do in Rails. See the documentation for additional config.

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react-rails

react-rails should be used in all Rails apps that use React. It provides the perfect amount of glue between Rails conventions and React.

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rails-assets

rails-assets should be considered for bundling js/css assets into your applications. The most popular React-libraries we use are registered on Bower and can be easily added through Bundler and react-assets.

caveats: rails-assets gives you access to bower projects via Sprockets requires. This is a win for the traditionally hand-wavy approach that Rails takes with JavaScript. This approach doesn't buy you modularity or the ability to interop with JS tooling that requires modules.

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flux

Use Alt for flux implementation. Alt is true to the flux pattern with the best documentation available.

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