Components should be assigned to variables whose name will be the components name used throughout the application. In JSX:
var Component = React.createClass({});
Compiles to:
var Component = React.createClass({displayName: "Component"});
This helps with modulatity in your application - Export/Require (Component.jsx example):
var Component = React.createClass({});
module.export = Component;
define([],function(){
var Component = React.createClass({});
return Component;
});
Order component methods based on the order of their life-cycle methods:
var Component = React.createClass({
propTypes: {},
mixins : [],
getInitialState: function() {},
getDefaultProps: function() {},
componentWillMount: function() {},
componentWillReceiveProps: function() {},
componentWillUnmount: function() {},
// Begin custom methods
_customHelperMethods: function() {},
_customDerivedPropertiesMethods: function() {},
_customEventMethods: function() {},
_customRenderMethods: function() {},
// End with render
// Locate quickly and understand components internal elements and structure
render: function() {}
})
Prefix custom functions with an underscore to distinguish between custom methods and methods which are part of React's API (example Component.jsx):
var Component = React.createClass({
propTypes: {},
getInitialState: function() {},
componentWillReceiveProps: function() {},
_computePrice : function() {},
_onChange : function() {},
_renderButtonGroup : function() {},
render : function() {}
});
Note: Keep the render functions at the bottom of your component declarations. This way, you can always expect to find it in the same place.
// Childless components should close themselves
<childless />
// Components with children should have closing tags
<with-children><child/></with-children>
Always pass specifically need/required props and not all props to components/sub-components:
bad
<SubComponent {...this.props} />
good
<SubComponent theData={this.props.theData} />
<SubComponent {...this.props.theData} />
If there are multiple component attributes, display them on newlines and indent them instead of keeping them in-line:
bad
<Component attribute={...} anotherAttribute={...} attributeThree={...} attributeFour={...} attributeFive={...} attributeSix={...} attributeSeven={...}/>
good
<Component attribute={...}
anotherAttribute={...}
attributeThree={...}
attributeFour={...}
attributeFive={...}
attributeSix={...}
attributeSeven={...}
/>
Set propTypes for validation and self-documentation, required first:
propTypes: {
arrayOfProps: React.PropTypes.arrayOf(React.PropTypes.object).isRequired,
arrayProp: React.PropTypes.array,
boolProp: React.PropTypes.bool,
funcProp: React.PropTypes.func,
numProp: React.PropTypes.number,
objProp: React.PropTypes.object,
stringProp: React.PropTypes.string
}
Avoid using React.PropTypes.object and React.PropTypes.array if you can be more explicit:
propTypes: {
message: React.PropTypes.instanceOf(Message),
someView: React.PropTypes.shape({
numProp: React.PropTypes.number.isRequired,
funcProp: React.PropTypes.func
}),
optionalUnion: React.PropTypes.oneOfType([
React.PropTypes.string,
React.PropTypes.number
]).isRequired,
arrayOfProps: React.PropTypes.arrayOf(React.PropTypes.shape({
arrayProp: React.PropTypes.array,
boolProp: React.PropTypes.bool,
})),
customProp: function(props, propName, componentName) {
if (!/matchme/.test(props[propName])) {
return new Error('Validation failed!');
}
}
}
Keep indenting consistent for JSX which contains nested elements across multiple lines, no matter how few elements are returned. Always use enclosing parens around JSX blocks. This helps preserve readability:
bad
return <div><ComponentOne /><ComponentTwo /></div>;
good
return (
<div>
<ComponentOne />
<ComponentTwo />
</div>
);
Ternaries are fine as long as they fit on one line without scrolling:
{this.state.on ? ‘On’ : ‘Off’}
When an element returned by render depends on state, props, or other conditions, declare it in a var at the top of the render function:
either the element will be rendered, or it won't be.
var optionalElement;
if (this.props.condition) {
optionalElement = (<div> … </div>);
}
return (
<div>
…
{optionalElement}
…
</div>
);
It can be useful to keep a consistent suffix on these variables so they are easily identifiable:
optionalButtonElement, optionalFormElement, optionalTabElement
Do NOT use &&.
bad
return (
<div>
…
{this.props.condition && (<div> … </div>)}
…
</div>
);
Create lists inline with map calling a render method and ALWAYS assign a unique key:
_renderListItem: function(item) {
// Keep the key as the first attribute so it's readily identifiable.
return (<Component key={item.key} data={item.data} />);
},
render: function() {
return (
<div>
{this.props.list.map(this._renderListItem)}
</div>
);
}
Form elements can be written with an onChange handler to avoid having to register onChange on every field (within the same form):
<form onChange={this.inputHandler}>
...
<input type="text" name="newDinosaurName" value={this.state.newDinosaurName} />
...
</form>
where the inputHandler looks like:
function(event) {
actions.propagateValue({
field : event.target.name,
value : event.target.value
});
}
Props are:
- never modified by the component itself (directly)
- set and modified by the parent
State should:
- be set by the component
- never set by an external source
- only be determined by props if a prop is explicitly an initial state i.e.
<Foo initialCount=3/> - be kept as high up in the component hierarchy as reasonable
- never be duplicated or kept "in sync" between siblings
Derived properties should be moved into a component method.
Given this:
propTypes: {
myList: React.PropTypes.arrayOf(React.PropTypes.string).required
},
getInitialState: function() {
return {
title: 'WAT',
filterString: ''
}
},
...
bad
render: function() {
return (
<h1> { title.substr(0,20) } </h1>
<ul>
{ this.props.myList.filter(function(item) { return item.matches(this.state.filterString); }).map(function(item) {
<li>{ item }</li>
})}
</ul>
);
}
good
_shortTitle: function() {
return title.substr(0,20);
},
_filteredList: function() {
return this.props.myList.filter(function(item) {
return item.matches(this.state.filterString);
});
},
render: function() {
return (
<h1>{ _shortTitle() }</h1>
<ul>
{ this._filteredList().map(function(item) {
<li>{ item }</li>
})}
</ul>
);
}
Derived properties can/should be memoized with an important caveat: Memoization is only practical with immutable objects and arrays. Immutability is recommended in general.
When binding functions inside a collection, bind to the key instead of the data object itself. This helps keep logic out of the view.
React will currently override event handler binds to bind to this. This practice will stop in React 13, so you should explicitly bind to this from now on.
Don't use data- and dataset in event handlers/binds. It's terribly slow and non-reacty.
Avoid using the event object in event handlers unless you need something on the event object. If you need to call event.preventDefault(), use a prevent default wrapping utility function.
bad
...
_doSomething: function(event) {
event.preventDefault();
var i = event.target.dataset.id;
...
},
render: function() {
return this.props.sections.map(function(section, i) {(
<a key={ i } href="#" onClick={ _doSomething } data-id="i">{ section.label }</a>
)});
}
good
...
_preventDefault: function(handler) {
return function(event) {
event.preventDefault();
handler.call(this, event);
};
},
_doSomething: function(i) {
...
},
render: function() {
return this.props.sections.map(function(section, i) {(
<a key={ i } href="#" onClick={ preventDefault( _doSomething.bind(this, i) }>{ section.label }</a>
)});
}
Note: event.stopPropagation could be wrapped similarly. These wrapping functions should probably go into some mixin.
Don't use varargs in event handlers. The event object will get appended to arguments when bind is used.
Mixins provide additional functionality and help keep components DRY. However, they also "hide" code relevant to the component.
TODO:
Initially Forked from the React Style Guide. Thank you for starting DeepAnchor!