The project has the following reference, which returns a string:
const left = slide.imageLeft; // introLeft
And further renders it inside React Component. But it returns as a string styles.imageLeft and since webpack doest convert it into corresponding bundled class like 914u923asdsajdlj1l23 the styles are not applied.
<div className={`styles.${left}`}> </div>
P.S I did try to eval, but it drops 2 errors.
There is an internal error in the React performance measurement code. Did not expect componentDidMount timer to start while render timer is still in progress for another instance.
And
ReferenceError: styles is not defined
Can you please suggest the possible ways to achieve dynamic class generation for css-loader.
You have to define the style within the render(), or within the component definition, like this
render: function(){
var myStyle = {
// your style rules go here
};
return(
<div style={myStyle}>
{this.props.children}
</div>
)
}
in a way, this is already dynamic, because all you have to do is to change to style and it'll make sure that the component will re-render on update
Related
For example - add animate-ping upon new message from a web-socket.
Tailwind just-in-time is likely to be the reason why you can't do that.
Basically, if animate-ping is not scraped in your files, adding it through Javascript or any other way later will simply not work, as the CSS file generated will not include animate-ping.
You should likely make your very own class in your CSS, even if it means using #apply directive of Tailwind. Adding Tailwind class later on in the DOM that were never parsed at build time will simply.. not works.
To conditionally show a class would be something like this:
function Notification() {
const [isNotification, setIsNotification] = useState(false);
return (
<div className={` ${isNotification ? "animate-ping" : null} h-2 w-2 m-5 bg-sky-400 rounded-full`}></div>
);
}
How can I change the className or style of a div without using state or any third party libraries? Lets say I click on a button, and I need to change the background color of a div how can I do that?
<Affix onChange={() => change css or class} offsetTop={60}>
<div>...</div> // Change css of this div
</Affix>
You can change any attribute or property of a Component (Element) in React by using basic javascript functions.
onClick={(e) => {
e.currentTarget.setAttribute("src", newUrl);
}
Will change an image the moment you click on it, without using Ref or State.
event.currentTarget will give you the reference to the component that fired that particular React.MouseEventHandler event, and with the Element's reference, you can manipulate it at will.
This is particularly useful when you need to change an attribute in a component in a map loop without needing to keep track of it.
Edit:
A friend of mine just gave me a better one for classes in specific:
e.currentTarget.classList.add('my_custom_klass')
You can either do it manually using state:
const [myClass, setMyClass] = useState('bgColor-white');
return (
<Affix onChange={() => setMyClass('bgColor-black')} offsetTop={60}>
<div className={myClass}>...</div> // Change css of this div
</Affix>
)
Or you can use a library that handles dynamic styling. I use and recommend styled-components
I have a Search parent component and a SideBar child component, I am trying to get context in SideBar, but everytime it returns empty.
I followed the tutorial exactly like: https://itnext.io/manage-react-state-without-redux-a1d03403d360
but it never worked, anyone know what I did wrong?
Here is the codesandbox link to the project: https://codesandbox.io/s/vigilant-elion-3li7v
I wrote that article.
To solve your specific problem:
When using the HOC withStore you're injecting the prop store into the wrapped component: <WrappedComponent store={context}.
The value of the prop store is an object that contains 3 functions: get, set, and remove.
So, instead of printing it, you should use it. For example this.props.store.get("currentAlbums") or this.props.store.set("currentAlbums", [album1, album2]).
This example is forked by your code: https://codesandbox.io/s/nameless-wood-ycps6
However
Don't rewrite the article code, but use the library: https://www.npmjs.com/package/#spyna/react-store which is already packed, tested, and has more features.
An event better solution is to use this library: https://www.npmjs.com/package/react-context-hook. That is the new version of the one in that article.
This is an example of a sidebar that updates another component content: https://codesandbox.io/s/react-context-hook-sidebar-xxwkm
Be careful when using react context API
Using the React Context API to manage the global state of an application has some performance issues, because each time the context changes, every child component is updated.
So, I don't recommend using it for large projects.
The library https://www.npmjs.com/package/#spyna/react-store has this issue.
The library https://www.npmjs.com/package/react-context-hook does not.
You pass the store as a prop, so to access it, you need this.props.store in your SideBar.
Not this.state.store
Create a wrapping App component around Search and Sidebar:
const App = props => (
<div>
<Search />
<SideBar />
</div>
);
export default createStore(App);
Now you can manipulate state with set and get that you have available in child components Search and Sidebar.
In Search component you can have something like:
componentDidMount() {
this.props.store.set("showModal", this.state.showModal);
}
also wrapped with withStore(Search) ofc.
and in SideBar you can now call:
render() {
return (
<div>
{"Sidebar: this.state.store: ---> " +
JSON.stringify(this.props.store.get("showModal"))}
}
</div>
);
}
and you will get the output.
I have a large React app and I have a few components that I would like to completely disable from a config or global level. Is there any kind of global hook that I can use that is called before any component is rendered? If so, I imagine I can check the name of the component and return null if the name is on the disabled list. How would you do this?
There are a lot of ways to do this:
React's Context API allows you pass props through every level of the component tree so you can use them as flags to enable/disable components. Should be used sparingly however.
Higher Order Components are basically just functions that return a component. You could wrap your components in logic to render them as needed.
Or of course you could use a global state manager like redux to set global states.
There are many ways to do this, so, I'll just describe one simple way: using references and updating the states accordingly.
Full working feature hide/showing sandbox online: codesandbox.io ReactJS Feature Hide/Show Demo
Defined are two classes, class Feature extends React.Component and class App extends React.Component. The render() for <Feature/> is...
render() {
if (!this.state.enabled) {
return <div />;
}
return (
<div className="Feature">
<h1>My Feature!</h1>
</div>
);
}
And the option for enabling/disabling a feature in <App /> would handle display/hiding like so...
handleOnClick(e) {
if (e.target.checked) {
this.feature.setState({ enabled: true });
} else {
this.feature.setState({ enabled: false });
}
}
Of course, you need to make sure that <Feature /> has the reference set...
<Feature
ref={instance => {
this.feature = instance;
}}
/>
If you need simplest solution just use browser global vars and check it in render.
render() {
if( window.globalFlag ) return null
return (
<div> feature content...
Drawbacks:
modifying component,
using global scope,
some unnecessary code can be run earlier (f.e. constructor) and later (f.e. componentDidMount).
Use HOCs - wrap your component - connecting with global store using redux or context API.
<FlagsProvider store={flagStore}>
<SomeComponent_1>
<SomeComponent_2>
<FlagsConsumer flag="someFeatureFlag">
<SomeFeatureComponent />
<FlagsConsumer/> connects to store (redux connect would be an inner wrapper - composing HOCs) and conditionally renders <SomeFeatureComponent /> (or null).
Of course HOC can pass received props to wrapped component - it can be functionally transparent.
Don't reinvent the wheel - use some ready module, read tutorials, google for sth suitable.
HOC can also play a role of A/B testing.
with React v0.12 the #jsx pragma is gone which means it is no longer possible to output jsx with anything other than the React.METHODNAME syntax.
For my use case I am trying to wrap the React object in another object to provide some convenience methods thus, in my component files, I want to be able to write:
var myConvenienceObject = require('React-Wrapper');
var Component = myConvenienceObject.createSpecializedClass({
render: function () {
return <div />
}
})
However the jsx compiler automatially converts <div /> into React.createElement("div", null)
With older versions of React it was possible to handle this using the pragma at the top of the file. However, since that has been removed, I was wondering if there was any way currently to change the name of the object compiled by jsx so <div /> would be transformed into myConvenienceObject.createElement("div", null)
No, it's no longer possible to use a custom prefix for JSX. If you need to do this, you'll need to modify the JSX transform code, or create a fake React.
var React = require('react'), FakeReact = Object.assign({}, React, {
createElement: function(component, props, ...children){
// ...
// eventually call the real one
return React.createElement(component, props, ...children);
}
});
module.exports = FakeReact;
And then to use it you import the fake react and call it React.
var React = require('fake-react');
// ...
render: function(){ return <div />; }
If you would like to make some elements contains in your myConvenienceObject, you could consider the children props as shown in the doc. But this may need some changes in the myConvenienceObject too, to accept the children.
By the way, i'm not sure where is this createSpecializedClass functions comes from and what it does