react-loadable-component
v1.0.0
Published
A higher order component for loading components with promises
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Readme
react-loadable
A higher order component for loading components with promises.
- Returns
null
until after adelay
(default: 200ms) - Returns
<LoadingComponent/>
afterdelay
and beforeloader()
is successful - Caches
Component
returned byloader()
on success - Shows optional
<ErrorComponent/>
any time theloader()
fails until it succeeds. - Avoids flashing states when it doesn't need to.
- Designed around module bundlers like Webpack (async imports work statically)
- Supports server-side rendering via a dynamic
require()
- Eagerly preload components when needed
- Support for requiring synchronously from webpack when available
Example Project: https://github.com/thejameskyle/react-loadable-example
Introductory blog post: https://medium.com/@thejameskyle/react-loadable-2674c59de178#.6h46yjgwr
Results
- "Webpack 2 upgrade & react-loadable; initial load from 1.1mb to 529kb in under 2 hours. Immense."
- "Oh hey - using loadable component I knocked 13K off my initial load. Easy win!"
- "Had a look and its awesome. shaved like 50kb off our main bundle."
Example
// @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 ? <div>Loading...</div> : null; // Don't flash "Loading..." when we don't need to.
} else if (error) {
return <div>Error! Component failed to load</div>;
} 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 <LoadableMyComponent/>;
}
}
API
Loadable({
loader: () => Promise<React.Component>,
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.
type Props = {
isLoading: boolean,
error: Error | null,
pastDelay: boolean,
};
let MyLoadingComponent = ({isLoading, error, pastDelay}: Props) => {
if (isLoading) {
return pastDelay ? <div>Loading...</div> : null; // Don't flash "Loading..." when we don't need to.
} else if (error) {
return <div>Error! Component failed to load</div>;
} 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).
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.
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.
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 ofpreload()
. It's meant as a performance optimization, not for creating UI logic.
Example:
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 (
<div>
<button onClick={this.onClick} onMouseOver={this.onMouseOver}>
Show loadable component
</button>
{this.state.showComponent && <LoadableMyComponent/>}
</div>
)
}
}
Babel Plugin
Included in the react-loadable
package is a Babel plugin that can add
serverSideRequirePath
and webpackRequireWeakId
for you.
Input:
import Loadable from 'react-loadable';
Loadable({
loader: () => import('./MyComponent'),
LoadingComponent: () => null,
});
Output:
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:
{
plugins: [
["react-loadable/babel", {
server: true,
webpack: true
}]
]
}
Options:
server
(default:true
) - Whentrue
addsserverSideRequirePath
config.webpack
(default:false
) - Whentrue
addswebpackRequireWeakId
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
.
let LoadableMyComponent = Loadable({
loader: () => import('./MyComponent'),
serverSideRequirePath: path.join(__dirname, './MyComponent'),
webpackRequireWeakId: () => require.resolveWeak('./MyComponent'),
// ...
});
But why couldn't it just be a string?
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.
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.
import MyLoadable from './MyLoadable';
let LoadableMyComponent = MyLoadable({
loader: () => import('./MyComponent'),
});
export default class Application extends React.Component {
render() {
return <LoadableMyComponent/>;
}
}