A higher order component for loading components with promises
npm install react-loadable-componentreact-loadablenull until after a delay (default: 200ms)
delay and before loader() is successful
Component returned by loader() on success
loader() fails until it succeeds.
require()
js
// @flow
import path from 'path';
import React from 'react';
import Loadable from 'react-loadable';
type Props = {
isLoading: boolean,
error: Error | null,
pastDelay: null,
};
let MyLoadingComponent = ({isLoading, error, pastDelay}: Props) => {
if (isLoading) {
return pastDelay ? Loading... : null; // Don't flash "Loading..." when we don't need to.
} else if (error) {
return Error! Component failed to load;
} else {
return null;
}
};
let LoadableMyComponent = Loadable({
loader: () => import('./MyComponent'),
LoadingComponent: MyLoadingComponent,
// optional config...
delay: 200,
serverSideRequirePath: path.join(__dirname, './MyComponent'),
webpackRequireWeakId: () => require.resolveWeak('./MyComponent'),
});
export default class Application extends React.Component {
render() {
return
}
}
`
API
`js
Loadable({
loader: () => Promise,
LoadingComponent: React.Component,
// optional options...
delay?: number = 200,
serverSideRequirePath?: string,
webpackRequireWeakId?: () => number,
})
`
#### opts.loader
Function returning promise returning a React component displayed on success.
Resulting React component receives all the props passed to the generated
component.
#### opts.LoadingComponent
React component displayed after delay until loader() succeeds. Also
responsible for displaying errors.
`js
type Props = {
isLoading: boolean,
error: Error | null,
pastDelay: boolean,
};
let MyLoadingComponent = ({isLoading, error, pastDelay}: Props) => {
if (isLoading) {
return pastDelay ? Loading... : null; // Don't flash "Loading..." when we don't need to.
} else if (error) {
return Error! Component failed to load;
} else {
return null;
}
};
`
If you don't want to render anything you can pass a function that returns
null (this is considered a valid React component).
`js
Loadable({
loader: () => import('./MyComponent'),
LoadingComponent: () => null,
});
`
#### opts.delay (optional, defaults to 200, in milliseconds)
Only show the LoadingComponent if the loader() has taken this long to
succeed or error.
#### opts.serverSideRequirePath (optional)
When rendering server-side, require() this path to load the component
instead, this way it happens synchronously. If you are rendering server-side
you should use this option.
If you are using Babel, you might want to use the Babel plugin
to add this option automatically.
#### opts.webpackRequireWeakId (optional)
In order for Loadable to require() a component synchronously (when possible)
instead of waiting for the promise returned by import() to resolve. If you
are using Webpack you should use this option.
`js
Loadable({
// ...
webpackRequireWeakId: () => require.resolveWeak('./MyComponent')
});
`
If you are using Babel, you might want to use the Babel plugin
to add this option automatically.
#### opts.resolveModule (optional)
If the component that you want to load is not the default exported from a module
you can use this to function to resolve it.
`js
Loadable({
// ...
resolveModule: module => module.MyComponent
});
`
#### Loadable.preload()
The generated component has a static method preload() for calling the loader
function ahead of time. This is useful for scenarios where you think the user
might do something next and want to load the next component eagerly.
> Note: preload() intentionally does not return a promise. You should not
> be depending on the timing of preload(). It's meant as a performance
> optimization, not for creating UI logic.
Example:
`js
let LoadableMyComponent = Loadable({
loader: () => import('./MyComponent'),
LoadingComponent: MyLoadingComponent,
});
class Application extends React.Component {
state = { showComponent: false };
onClick = () => {
this.setState({ showComponent: true });
};
onMouseOver = () => {
LoadableMyComponent.preload();
};
render() {
return (
{this.state.showComponent &&
)
}
}
`
Babel Plugin
Included in the react-loadable package is a Babel plugin that can add
serverSideRequirePath and webpackRequireWeakId for you.
Input:
`js
import Loadable from 'react-loadable';
Loadable({
loader: () => import('./MyComponent'),
LoadingComponent: () => null,
});
`
Output:
`js
import _path from 'path';
import Loadable from 'react-loadable';
Loadable({
loader: () => import('./MyComponent'),
LoadingComponent: () => null,
serverSideRequirePath: _path.join(__dirname, './MyComponent'),
webpackRequireWeakId: () => require.resolveWeak('./MyComponent'),
});
`
#### Plugin Setup
If you have react-loadable installed already, all you need to do is add this
plugin to your Babel config:
`js
{
plugins: [
["react-loadable/babel", {
server: true,
webpack: true
}]
]
}
`
Options:
- server (default: true) - When true adds serverSideRequirePath config.
- webpack (default: false) - When true adds webpackRequireWeakId config.
FAQ
#### Why are there multiple options for specifying a component?
The standard loader option is the only required option for specifying a
component. However, to enable server-side rendering you need
serverSideRequirePath and to optimize Webpack loading you need to specify
webpackRequireWeakId.
`js
let LoadableMyComponent = Loadable({
loader: () => import('./MyComponent'),
serverSideRequirePath: path.join(__dirname, './MyComponent'),
webpackRequireWeakId: () => require.resolveWeak('./MyComponent'),
// ...
});
`
But why couldn't it just be a string?
`js
let LoadableMyComponent = Loadable({
Component: './MyComponent',
// ...
});
`
The reason is that tools like Webpack and Browserify rely on static analysis to
determine how to bundle your code. When it sees code like import('module') it
adds it to the module graph.
When you just have a string like "./MyComponent", these tools don't know the
difference between that and any other string.
For server-side rendering we need to have an exact file path so that we can
require() it synchronously. We don't specify require('./MyComponent')
directly because that would add it to the bundle in Webpack or Browserify.
For webpackRequireWeakId it needs to be a function because
require.resolveWeak does not exist in any tool other than Webpack.
If you are using Babel, you might want to use the Babel plugin
to add these options automatically.
#### How do I avoid repetition?
Specifying the same LoadingComponent or delay every time you use
Loadable() gets repetitive fast. Instead you can wrap Loadable with your
own Higher-Order Component (HOC) to set default options.
`js
import Loadable from 'react-loadable';
import MyLoadingComponent from './MyLoadingComponent';
export default function MyLoadable(opts) {
return Loadable({
LoadingComponent: MyLoadingComponent,
delay: 200,
...opts
});
}
`
Then you can just specify a loader when you go to use it.
`js
import MyLoadable from './MyLoadable';
let LoadableMyComponent = MyLoadable({
loader: () => import('./MyComponent'),
});
export default class Application extends React.Component {
render() {
return
}
}
``