Over on this question, it is answered how to bind a component to browser resize events. I'd like to create an HOC/decorator function to elegantly add this behaviour to Components in my Component Library so that I can be dry about adding this behaviour.
I was able to use the inverted HOC pattern to create a higher-order-component that will essentially attach the base components onResize method to a (resize) event listener:
import React from 'react';
import debounce from 'debounce';
import getDisplayName from 'recompose/getDisplayName'
export const withOnResize = BaseComponent => (
class ResizeEnhanced extends BaseComponent {
static displayName = getDisplayName(BaseComponent);
componentWillMount() {
this.debounce = debounce(this.onResize, 200);
window.addEventListener('resize', this.debounce);
if (super.componentWillMount) super.componentWillMount();
}
componentWillUnmount() {
window.removeEventListener('resize', this.debounce);
if (super.componentWillUnmount) super.componentWillUnmount();
}
render() {
return super.render();
}
}
);
and then the usage in some other component file:
export default withOnResize(MyComponent); // MyComponent has an onResize method.
--
This is sub-optimal at least because there is a dodgy reliance on the base component having an onResize method.
Is there a functional approach that would allow easily connecting resize listener and lifecycle events to a method on base components?
Obviously another option is to use something like Redux, and build the global events into the store - dispatching as required. Or even context if I was willing to re-render my entire app on context change, but I'm more interested in doing this at the component decoration level at this stage.
Related
I wrote a component Foo in React.js (its parameter "interface" consists of a single parameter text; there are more parameters in my real code):
import React from 'react';
export default class Foo extends React.Component {
constructor(props){
super(props);
}
render(){
return <div>{this.props.text}</div>;
}
}
and I thought I could improve the code by modifying the property access as:
import React from 'react';
export default class Foo extends React.Component {
constructor(props){
super(props)
this._text = props.text
}
render(){
return <div>{this._text}</div>;
}
}
This would give me the benefits that
I can immediately see what properties are supported by having a look at the constructor.
The code that applies the properties gets shorter/better to read.
However, this destroys the update workflow for the property. In a parent component I use Foo like
<Foo text={this.state.parentText}/>
and
this.setState({parentText: "new text"})
does not trigger an update of the text in Foo any more. The constructor of Foo is only called once and therefore, the private variable this._text is not updated on property changes.
=> Using extra private properties to modify the parameter access turned out to be a bad idea.
=> What would you recommend to have a clear interface for the component without breaking the update workflow?
Some ideas:
a) List all used properties at the start of render (and componentDidUpdate)
render(){
const text = this.props.text;
return <div>{text}</div>;
}
b) Create a getter for each property and put them directly under the constructor, for example
get _text(){
return this.props.text;
}
c) (Only for shorter access.) Try to avoid class components. With function components there is direct access with props.text instead of this.props.text. Or, as a workaround, inherit from a custom component class that passes props argument to render:
render_props(props){
...
}
(Why doesn't react pass this.props as an argument to render by default?)
d) Document the supported properties in a doc string
=> If you know a better option / some standard / best practice, please let me know.
Also tried but failed:
I tried to use state in the child component, with the hope that it would be automatically updated on updates of the parent state:
import React from 'react';
export default class Foo extends React.Component {
constructor(props){
super(props)
this.state = {
text: props.text
}
}
render(){
return <div>{this.state.text}</div>;
}
}
However, this also breaks the update workflow. Using this.state only seems to make sense in the parent component.
Related:
Can I update a component's props in React.js?
https://github.com/vasanthk/react-bits/blob/master/anti-patterns/01.props-in-initial-state.md
Related topic:
How to interact with third party libraries using function components?
https://reactjs.org/docs/integrating-with-other-libraries.html
How do I use/include third party libraries in react?
Integrating React with Other Libraries
Use function components for React >= 16.8, also see recommendation at
https://www.w3schools.com/react/react_class.asp
Use useState hooks instead of setState. This is the modern way to write React, and gives you a simpler way to access state (foo.text, foo.setText). https://reactjs.org/docs/hooks-state.html
Typescript would help with docs (type props = { text: string }), but I also would like the answer for d) (your question is several questions I think).
Use props.text directly, instead of using extra shortcut variable const text = props.text suggested by option a). This way, you don't have a list of all available properties on top of the component function. However, using a consistent props. prefix makes it easier to spot the injected variables in the react code. If there is a huge number of properties and its hard to identify them, try to improve modularization.
JavaScript example code:
Child component Foo:
import React from 'react';
export default function Foo(props){
return <div>{props.text}</div>;
}
}
Parent component:
import React, { useState } from 'react';
import Froo from './foo';
export default function Parent(){
const [parentText, setParentText] = useState('Hello world');
return <Foo text={parentText}/>;
}
ReactJS is a great library, However, it misses some features which I found in Vue and Angular. These features can be implemented of course in React, however, they require extra code to be written.
Every react component, or every JSX element I should say has the following properties shared, which are given by React to us to consume:
ref
key
I wanted to add extra props:
renderIf
fallback
These props help in a way I can't describe when it comes to conditional rendering and filtering the views based on the logged-in user permissions and roles (and other conditional rendering use cases, of course).
In react, if we wanted to apply these props to our components, we would use a HOC as follows:
// 🍎 Disclaimer: you don't have to understand any of the code written bellow, the general idea is that this is a HOC.
import React from 'react'
import getVal from './getVal'
export default function EnhancedComponent(OriginalComponent) {
return ({ renderIf: renderIf_ = true, override: override_, fallback: fallback_ = undefined, ...props }) => {
const renderIf = getVal(renderIf_)
const override = getVal(override_)
const fallback = getVal(fallback_)
const consumersComponent = <OriginalComponent {...props} />
let render = fallback
if (renderIf) render = consumersComponent
if (override_ !== undefined) render = override
return render
}
}
Where every time you want to apply these props to your components, you would have to wrap every new component you create with EnhancedComponent as follows:
export default EnhancedComponent(function Sidenav(){
return <div> side nav </div>
})
Now, you can use your Sidenav component within your App component as follows:
import Sidenav from './Sidenav'
export default function App(){
return (
<div>
<Sidenav renderIf={(5 + 5 === 10)}/>
<div>etc</div>
</div>
)
}
This API is great, but it has a drawback, which is, every time you want to apply these cool props (renderIf and fallback) you'll have to repeat these steps:
import Enhanced component to your file.
wrap your export with Enhanced component.
What I am looking for, is a method, or a way to inherit, or to add some props to the original react component class, somehow?
In react class components, I can imagine doing this on the React.Component class which we used to extend from in the past
class Car extends React.Component{
constructor(){}
render(){
return <div>I miss you 🌹</div>
}
}
But in react functional component, how can we do that?
I want to apply these props by default everytime I create a new component, without wrapping my components in a HOC everytime.
Does React have a way to do that? To change its defaults ?
For example I could have a component
class HomeDefault extends PureComponent {
...
}
and I could add a property after the instance like so before the export
HomeDefault.someProperty = {test: 'test'}
Now if I were to use something like a higher order component over my HomeDefault component, I could console log out this "someProperty" object that I just set.
export default withHOC(HomeDefault)
// withHOC.js
import React from 'react';
const withHOC = Component => {
const WithHOC = props => {
console.log("the property: ", Component.someProperty) // this will work with the example above
return <Component />;
};
return WithHOC;
};
export default withNavigation;
So THAT works, but I need a solution that can set this property from within a useEffect (for functional components) or a componentDidMount (for class)
Is this possible??
The actual use case is that I'm upgrading react navigation and the .navigationOptions property has been done away with but I'm trying to not completely redo our code for the time being. So it would be awesome t run a function in a useEffect/componentDidMount and set this property that way since navigationOptions doesn't make the navigation state available outside of the component.
I hope this all makes sense! thank you all
I have more than 20 components in my react project. So doing the same thing for every component would be so unwise, so from oop concepts if I create a class with all the functionalities, then I can use it for all the objects I want.
In my case, I want to check if a user is logged in or not. If not redirect to '/login'. Now I have 'NavigationBar' inside each component, where I'm writing some code to redirect or not. But for a few seconds I can see then snap of each components, especially those large ones.
This is not also wise step
So here is what I tried next, created a component named Core extending React.Component, then I extended all component from it, but it gives me error directly.
What is the actual problem here? How this can be solved?
codesandbox.io
just add this line to Child.js
import React from "react";
React doesn't allow creation of component by subclassing defined component, the only way to create component is to extends directly the React.Component class, But react allow you to add extra behavior to defined component by using Higher-Order Components which has purpose to alter defined component by adding wrapper to and existing component
function wrapper(WrappedComponent) {
return class extends React.Component {
render() {
// Here you can add any logic you want
return (<div>
// Here you can add extra code
<h1>Code rendered by wapper</h1>
<WrappedComponent {...this.props} />;
</div>
}
}
}
And you use it like this
import wrapper from './wrapper';
import Child from './Child';
const HigherWrapper = wrapper(Child);
const rootElement = document.getElementById("root");
ReactDOM.render(<HigherWrapper />, rootElement);
I'm new to ES6 and Redux. Im looking at some code and trying to understand what is going on in this new ES6 syntax.
I feel like this may be simple but i am not understanding it and it might help someone else in a similar position to me.
i want to know how the following code is creating a react element. im familiar with the React.createClass method, but that doesnt seem to be stated here or at least not explicitly. i can see React is imported, but it isnt mentioned in the rest of the code. so then how the FileTable get turned into a react component?
I can see the const variable FileTable seems to contain what would usually go in the render method of React.createClass, but if that is the case, where would methods like componentDidMount, componentDidUpdate, etc be defined?
Any help on this is greatly appreciated.
import React, { PropTypes } from 'react';
import { connect } from 'react-redux';
import * as actions from '../actions';
const FileTable = ({ fileList, getFileList}) => {
return (
<ul className="filterable-table">
{fileList.map((file)=><li>{file.fileName}</li>)}
</ul>
);
};
FileTable.propTypes = {
fileList: PropTypes.array,
};
const mapStateToProps = (state) => {
return {
fileList: state.fileList
};
};
const mapDispatchToProps = (dispatch) => {
return {
getFileList: () => dispatch(actions.getFileList())
};
};
export default connect(
mapStateToProps,
mapDispatchToProps
)(FileTable);
You can create react components in 3 ways - React.createClass, ES6 class or
Stateless (pure) function component. This is a stateless component, which means that it doesn't have state, life cycle methods (like componentDidMount or componentDidUpdate), and refs, and as you surmised it's similar to the render method of a react class.
Whenever you need a purely representational dumb component you can use a stateless component, due to its brevity. It goes nicely with redux, as the connect create a smart component that wraps the stateless method.
Regarding performance, stateless components don't have any performance gain over ES6 class component without state. However, Facebook stated that in the future there will be some optimizations.
It doesn't have to be declared here as a React component; React knows about pure functions.
Pure functions don't need to inherit from Component. They're not appropriate for all component types, but for simple HTML renders they're preferred (e.g., see eslint-plugin-react prefer-stateless-function.
Pure functions don't have component lifecycles, associated methods, etc.