I have to render multiple DOM elements from my JS.
Say I have divs like
<div id="div1"><div>
//Some Html tags
<div id="div2"><div>
//Some Html tags
<div id="div3"><div>
//Some Html tags
I need to render these three divs .
Each div will contain set of radio buttons. On click of any radio button in any div , I will execute a validation rest call , and based on the result I have to display only the valid radio buttons (that means I have to update each divs state.).
I used , something like this :
var divs=[
{"name":"one","element":"div1"},
{"name":"two","element":"div2"},
{"name":"three","element":"div3"}
];
for(var elem in divs){
ReactDOM.render(
<ElementBox name = {divs[elem].name} / > ,
document.getElementById(divs[elem].element)
);
}
But event handling is hectic if I use this kind of approach . Means I couldn't find any way to update other divs state after validation.
Is there any other way to render multiple containers in a single element ?
Yes there is: typical react is to only have 1 ReactDOM.render() to start the react-engine. And do all additional rendering within react components.
Something like this:
class ElementsBox extends React.Component {
render() {
return <div id={this.props.element}>{this.props.name}</div>
}
}
class ElementsContainer extends React.Component {
render() {
return (
<div>
{this.props.elements.map(function(element) {
return <ElementBox element={element} key={element.element}/>
});}
</div>
);
}
}
ReactDOM.render(<ElementsContainer elements={divs}/>,
document.getElementById('myreactrootinHTML'));
PS: unavoidable consequence of using react is that you always get a container within container, like this:
<div id='myreactrootinDOM'> // needs to be here so react can launch somewhere
<div> // react root can always only render 1 DOM element
<div id='div1'></div> // lower levels can have more than 1 component
<div id='div2'></div>
<div id='div3'></div>
</div>
</div>
Related
I'm in a learning phase of react and I've been trying to nest style of parent in component in child component via class in react.js. How to do it?
What I've tried until now:
function Card(props) {
const classes = 'card' + props.className;
return (
<div className={classes}>
{props.children}
</div>
)
}
export default Card
I applied style on class 'card' in a CSS file.
Parent component JS code:
import Card from './UI/Card';
function ExpenseItem(props){
return (
<Card className="expense-item">
<ExpenseDate date={props.date} />
<div className="expense-item__description">
<h2>{props.title}</h2>
<div className="expense-item__price">{`₹ ${props.amount}`}</div>
</div>
</Card>
)
}
Now, there are various classes in parent component that are styled accordingly. And I'd like to nest those classes in child component for those style to work.
You can see in the code the way I tried to nest the classes, but it isn't working.
const classes = 'card' + props.className;
What am I doing wrong? And how should I correct it?
You missed a space after the card class name, otherwise i don't see any other issues in your code. Try below, hope it works
const classes = 'card ' + props.className;
Just one note, this will make your components dependent on each other. One of best things about React is that it allows you to have separation of concerns. So Card component is doing Card component staff, displaying some information and needs not be dependent on a parent in this case ExpenseItem.
One way to do it is to use styled-components.
In my below code I want to render duplicate elements by using React.createRef(). because in the long run, I have to render the same element in the dialog for the help screen.
So how can I render it in DOM?
By the below code, I can get ref of the div element but cant renders it in Dom.
export default class TestComponent extends React.Component {
state = {};
myRef;
constructor(props) {
super(props);
this.myRef = React.createRef();
}
render() {
return (
<React.Fragment>
<div ref={this.myRef}>
<h2>Hello World!!!</h2>
</div>
{this.myRef && <>{this.myRef.current}</>}
</React.Fragment>
);
}
}
Edit:
I have to pass this reference to a new component(HelpScreenComponent), which will render same element along with some extra UI as a Dialog.
My problem was to render duplicate components on overlay for first-time users to display them a help screen.
I got not the exact answer but solution to my problem by rending only inner Html.
In the above code by replacing line
{this.myRef && <>{this.myRef.current}</>}
with this
{this.myRef.current && <div dangerouslySetInnerHTML={{__html: this.myRef.current.innerHTML}}/>}
I'm creating a React app on Rails and have encountered a problem regarding key assignment to dynamic children.
Below is a pared-down copy of my code:
class Records extends React.Component {
render () {
var records =
this.props.data.map(function(record) {
return <div>
<Record key={record.id} data={record} />
</div>;
});
return (
<div>
{records}
</div>
);
}
}
class Record extends React.Component {
render () {
return (
<div>
<h1>Title: {this.props.data.title}</h1>
</div>
);
}
}
The code runs correctly except for the warning below that appears on the console:
Warning: Each child in an array or iterator should have a unique "key" prop.
Check the render method of `Records`.
I've followed the link contained within the warning to the React guide (http://facebook.github.io/react/docs/multiple-components.html#dynamic-children).
Though I feel I've implemented their recommendation that the key should always be supplied directly to the components in the array, not to the container HTML child of each component in the array, I still receive this warning in the console.
Does anyone have any ideas why? I completely appreciate any help you might provide!
The problem is that you should add the key props to the outer div, not to your Record instance.
var records =
this.props.data.map(function(record) {
return <div key={record.id}>
<Record data={record} />
</div>;
});
In fact, you don't need the wrapping div at all.
The warning is there because you need to add the key prop to the repeated element, and in your code you have a list of divs, each containing a Record (not a list of Records).
React asks you to do so to be able to "track" (identify) these divs which would be exactly the same without a way to identify them. React needs this ids to efficiently track DOM mutations (e.g. reordering them, removing them, etc)
Then, if you use ES6 (transpiled with Babel or similar) along with JSX you can just to this:
var records = this.props.data.map(record => <Record data={record} key={record.id} />)
In your code sample, the child in the is the surrounding <div> element, not the Record component which has the key property.
Your resulting HTML structure looks like this
<div>
<div><h1 key="1">...</h1></div>
<div><h1 key="2">...</h1></div>
<div><h1 key="3">...</h1></div>
</div>
So indeed React is correct, the collection does not have a unique key for the top-level element.
Your two options are:
(A) Add the key property to the surrounding <div> such that it looks like this
<div>
<div key="1"><h1>...</h1></div>
<div key="2"><h1>...</h1></div>
<div key="3"><h1>...</h1></div>
</div>
var records =
this.props.data.map(function(record) {
return <div key={record.id}>
<Record data={record} />
</div>;
Or
(B) Get rid of the surrounding <div> altogether as it's not needed.
var records =
this.props.data.map(function(record) {
return <Record key={record.id} data={record} />;
Side-note: React expects your render call to only return a single top-level element, so you only need a container element if you want to have multiple sibling elements in a render call.
I'm having trouble finding relevant documentation on how to remove UI components when using react. For example, there's a login form. The user clicks submit and now the form should be removed from the screen. How do I do this?
I've found unmountComponentAtNode, but that can only be invoked at the parent level. Am I supposed to have a parent node that is aware of all child state and loads them conditionally? Should all children have an "isHidden" attribute which renders the dom as hidden if true?
This must be basic but I don't see this in the react js tutorials. I found this stackoverflow post (react.js: removing a component) is this really the pattern? It kind of makes sense but it means that a large app will likely have an extremely complex Application parent class that manages maps of application state based on configuration.
It seems like i need to start defining application state as named maps. For example:
BaseApp: showHeader=true;showContent=true;
LoginState: showBaseApp=true;showLoginForm=true;
LoggedInState: showBaseApp=true;showFeed=true;
At any moment we would have to update all state maps and call the base class render method...
In my opinion your question isn't about removing component but about showing the right component. And yes - it can be done with a component state but with Flux/Redux store/reducer as well.
In your example with a login form after click on "Submit" we can change local state for the component and show another text like "The request was sent blah-blah-blah" or another component.
But you can do this by extracting component's local state to a store/reducer and it'll be work better in relatively big app. Nevertheless, it's really up to you where you want to store state.
I like to use a hide prop like so.
class AppCtrlRender extends React.Component {
render() {
let page = this.state.appState.currentPage;
let hideAbout = (page != 'about');
let hideHome = (page != 'home');
return (
<div id='AppCtrlSty' style={AppCtrlSty}>
<div id='allPageSty' style={allPageSty}>
<AboutPage hide={hideAbout} />
<HomePage hide={hideHome} />
</div>
</div>
);
}
}
export default class AboutPage extends React.Component {
render() {
if (this.props.hide) return null;
let aTime = (new Cache()).time.toString();
return (
<div style={AboutPageSty}>
React 0.14 ReFlux used for app state. This is the About Page.
<NavMenu /><br/><br/>
{aTime}
</div>
);
}
}
I've been hiding/showing react components by not rendering them, for example:
render: function() {
var partial;
if (this.state.currentPage === 'home') {
partial = <Home />;
} else if (this.state.currentPage === 'bio') {
partial = <Bio />;
} else {
partial = <h1>Not found</h1>
}
return (
<div>
<div>I am a menu that stays here</div>
Home Bio
{partial}
</div>
);
}
but just say that the <Bio/> component has lots of internal state. Everytime I recreate the component, it loses it's internal state, and resets to it's original state.
I know of course that I could store the data for it somewhere, and pass it in via props or just globally access it, but this data doesn't really need to live outside of the component. I could also hide/show components using CSS (display:none), but I'd prefer to hide/show them as above.
What's the best practice here?
EDIT: Maybe a better way to state the problem is to use an example:
Ignore React, and assume you were just using a desktop app that had a configuration dialog with a Tab component called A, which has 2 tabs, named 1 and 2.
Say that tab A.1 has an email text field and you fill in your email address. Then you click on Tab A.2 for a second, then click back to Tab A.1. What's happened? Your email address wouldn't be there anymore, it would've been reset to nothing because the internal state wasn't stored anywhere.
Internalizing the state works as suggested in one of the answers below, but only for the component and it's immediate children. If you had components arbitrarily nested in other components, say Tabs in Tabs in Tabs, the only way for them to keep their internal state around is to either externalize it somewhere, or use the display:none approach which actually keeps all the child components around at all times.
It just seems to me that this type of data isn't data you want dirtying up your app state... or even want to even have to think about. It seems like data you should be able to control at a parent component level, and choose to either keep or discard, without using the display:none approach and without concerning yourself with details on how it's stored.
One option would be to move the conditional inside the component itself:
Bio = React.createClass({
render: function() {
if(this.props.show) {
return <p>bio comp</p>
} else {
return null;
}
}
});
<Bio show={isBioPage} />
Whether this is "best practise" or not probably depends on the exact situation.
Unfortunately, style={{display: 'none'}} trick only works on normal DOM element, not React component. I have to wrap component inside a div. So I don't have to cascade the state to subcomponent.
<div className="content">
<div className={this.state.curTab == 'securities' ? 'active' : ''}>
<Securities />
</div>
<div className={this.state.curTab == 'plugins' ? 'active' : ''}>
<Plugins />
</div>
</div>
Looks like official documentation suggests hiding stateful children with style={{display: 'none'}}
The fundamental problem here is that in React you're only allowed to mount component to its parent, which is not always the desired behavior. But how to address this issue?
I propose the solution, addressed to fix this issue. More detailed problem definition, src and examples can be found here: https://github.com/fckt/react-layer-stack#rationale
Rationale
react/react-dom comes comes with 2 basic assumptions/ideas:
every UI is hierarchical naturally. This why we have the idea of components which wrap each other
react-dom mounts (physically) child component to its parent DOM node by default
The problem is that sometimes the second property isn't what you want
in your case. Sometimes you want to mount your component into
different physical DOM node and hold logical connection between
parent and child at the same time.
Canonical example is Tooltip-like component: at some point of
development process you could find that you need to add some
description for your UI element: it'll render in fixed layer and
should know its coordinates (which are that UI element coord or
mouse coords) and at the same time it needs information whether it
needs to be shown right now or not, its content and some context from
parent components. This example shows that sometimes logical hierarchy
isn't match with the physical DOM hierarchy.
Take a look at https://github.com/fckt/react-layer-stack/blob/master/README.md#real-world-usage-example to see the concrete example which is answer to your question (take a look at the "use" property):
import { Layer, LayerContext } from 'react-layer-stack'
// ... for each `object` in array of `objects`
const modalId = 'DeleteObjectConfirmation' + objects[rowIndex].id
return (
<Cell {...props}>
// the layer definition. The content will show up in the LayerStackMountPoint when `show(modalId)` be fired in LayerContext
<Layer use={[objects[rowIndex], rowIndex]} id={modalId}> {({
hideMe, // alias for `hide(modalId)`
index } // useful to know to set zIndex, for example
, e) => // access to the arguments (click event data in this example)
<Modal onClick={ hideMe } zIndex={(index + 1) * 1000}>
<ConfirmationDialog
title={ 'Delete' }
message={ "You're about to delete to " + '"' + objects[rowIndex].name + '"' }
confirmButton={ <Button type="primary">DELETE</Button> }
onConfirm={ this.handleDeleteObject.bind(this, objects[rowIndex].name, hideMe) } // hide after confirmation
close={ hideMe } />
</Modal> }
</Layer>
// this is the toggle for Layer with `id === modalId` can be defined everywhere in the components tree
<LayerContext id={ modalId }> {({showMe}) => // showMe is alias for `show(modalId)`
<div style={styles.iconOverlay} onClick={ (e) => showMe(e) }> // additional arguments can be passed (like event)
<Icon type="trash" />
</div> }
</LayerContext>
</Cell>)
// ...