Develop Reference

How to access the data from data* attribute using JavaScript?

Scenario: When the user clicks on it, the data should be passed into someFunction().
<span id="someid" onClick={() => someFunction()} data-video-page="some data" class="dot" />`
I tried using getAttributes(), querySelector() methods until now to get the data from data attributes. But one of them are working, in fact they are returning none.

There is a React.js tag in your question, so I'll assume that this is for using data-set in React.js.
For React.js, this is how data-set can be used if you want to pass the data to some function on a click event. You can also visit the live demo here: stackblitz
const handleClick = (event) => {
// Your data is stored in event.currentTarget.dataset
// Here we get the data by destructuring it
// The name video-page need to change to videoPage for JS rules
const { videoPage } = event.currentTarget.dataset;
console.log(videoPage);
// Result printed: "your data"
// You can also run someFunction(videoPage) here
};
export default function App() {
return (
<button data-video-page="your data" onClick={handleClick}>
TEST
</button>
);
}

A working snippet
const someFunction = console.log;
function App() {
return (
<span id="someid"
onClick={(e) => {
const videoPage = event.target.dataset['videoPage'];
someFunction(videoPage)
}}
data-video-page="some data"
className="dot"
>
click me
</span>
)
}
ReactDOM.render(<App />, document.getElementById('root'));
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.6.3/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.6.3/umd/react-dom.production.min.js"></script>
<div id="root"></div>

The data* attribute can be accessed using the getAttribute() method.
Example 1:
var data = document.getAttribute('data*');
Example 2:
var element = document.querySelector('div');
var data = element.getAttribute('data');

React dangerouslySetInnerHTML Inside Fragment

I have a use-case where I need to format some text in React and also render HTML.
Here is an example of what I'm currently trying to achieve:
import React, {Fragment} from "react";
import {renderToString} from "react-dom/server";
function FormatText(props) {
const lines = props.children.split('\n');
return lines.map((line, index) => (
<Fragment key={index}>
{line}{index !== lines.length - 1 && <br/>}
</Fragment>
));
}
const content = {
first: 'This is some text\nwith new\n\nline characters - 1',
second: 'This is some text\nwith new\n\nline <strong>characters - <sup>2</sup></strong>',
};
function App() {
return (
<ol>
<li>
<FormatText>{content.first}</FormatText>
</li>
<li dangerouslySetInnerHTML={{
__html: renderToString(<FormatText>{content.second}</FormatText>)
}}/>
</ol>
)
}
As you can see, I have some content which contains \n characters and HTML. Calling the renderToString function converts the HTML into encoded characters, which means the HTML is not rendered properly.
Is there a way to render HTML inside a react fragment.
Ideally I wanted to do the following (but it doesn't):
function FormatText(props) {
const lines = props.children.split('\n');
return lines.map((line, index) => (
<Fragment key={index} dangerouslySetInnerHTML={{__html: renderToString(
<Fragment>
{line}{index !== lines.length - 1 && <br/>}
</Fragment>
)}}>
</Fragment>
));
}

<Fragment> doesn't adds any node to DOM and so you can't do dangerouslySetInnerHTML on it. It is basically a functionality provided by React to avoid addition of extra node to DOM when you needed to return more than one from return in render. So, if something doesn't exists on real DOM, you can't do anything on it.
renderToString is generally used on node server. When doing server side rendering, you want to send the html from server to client. So, better avoid renderToString also.
The issue is that, html doesn't recognises \n for new line etc. It needs html tags. The approach to use FormatText is fine or you can simply convert the \n to br and then use dangerouslySetInnerHTML inside the <li> tag.
const content = {
first: 'This is some text\nwith new\n\nline characters - 1',
second: 'This is some text\nwith new\n\nline <strong>characters - <sup>2</sup></strong>',
};
function App() {
return (
<ol>
<li dangerouslySetInnerHTML={{
__html: content.first.replace(/\n/g, "<br/>")
}}/>
<li dangerouslySetInnerHTML={{
__html: content.second.replace(/\n/g, "<br/>")
}}/>
</ol>
)
}
ReactDOM.render(<App/>, document.getElementById("root"))
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.6.1/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.6.1/umd/react-dom.production.min.js"></script>
<div id="root"></div>
Hope it helps. Revert for any doubts.

Hi I guess it is not possible, only way hot to pass formated html into DOm is via dom element DIV.
Maybe this link could help you or point to
https://reactjs.org/docs/dom-elements.html

Why props alone are being used in called React function component?

I was learning React and I came to a point which created confusion. Everywhere I was using props while writing Function components.
I always use props.profile and it works fine. But in one code component, I had to write
const profiles=props; and it worked fine.
I tried using const profiles=props.profile; and also I tried using inside return in 'Card' function component
{props.profile.avatar_url} but both of them failed
Below is my code which works fine
const Card=(props)=>{
const profiles=props; //This I dont understand
return(
<div>
<div>
<img src={profiles.avatar_url} width="75px" alt="profile pic"/>
</div>
<div>
<div>{profiles.name}</div>
<div>{profiles.company}</div>
</div>
</div>
);
}
const CardList=(props)=>{
return(
<div>
{testDataArr.map(profile=><Card {...profile}/>)}
</div>
);
}
Can someone please help me understand why I can't use const profiles=props.profile?
What are the other ways to achieve the correct result?

Your testDataArr might be this,
testDataArr = [{avatar_url:"",name:"",company:""},{avatar_url:"",name:"",company:""},{avatar_url:"",name:"",company:""}]
Now when you do this,
{testDataArr.map(profile=><Card {...profile}/>)}
here profile = {avatar_url:"",name:"",company:""},
and when you do,
<Card {...profile}/>
is equivalent to,
<Card avatar_url="" name="" company=""/>
In child component, when you do this,
const profiles=props;
here props = {avatar_url:"",name:"",company:""}
So you can access it's values,
props.avatar_url
props.name
props.company
But when you do this,
const profiles=props.profile
profile key is not present in {avatar_url:"",name:"",company:""} object and it fails.

OK. Here is the issue, the props object does not contain a profile attribute, but IT IS the profile attribute. Becouse you are spreading the profile variable when you render the Card element (in the CardList), you basically are writing:
<Card avatarUrl={profile.avatarUrl} comapny={profile.comany} />
Instead, you should do
<Card profile={profile} />
and then in your Card component access the data this way
const Card = (props) => {
const profile = props.profile
}
or even simpler
const Card = ({profile}) => {
return <div>{profile.comany}</div>
}

Render or Use DocumentFragment in a React Component

I have a requirement in my React-based application to render dynamic forms. The form definitions are stored as JSON documents and I already have a JS library that parses the definitions and returns a DocumentFragment. This library is used in other non-React applications as well so I cannot change it.
To avoid re-writing the entire logic in my React application to parse the definitions and render the forms, I want to use the existing library.
My question is, what would be the best way to render the DocumentFragment in a React component?
Here is my DocumentFragment if I just output it to the console in my render() method.
#document-fragment
<fieldset id="metadata-form-908272" class="metadata-form-rendition hide-pages">
<div class="page-header-row">
<div class="page-header-cell">
<span>[Un-named page]</span>
<button class="page-header-button button icon">
<span class="icon icon-arrow-up-11"></span></button>
</div>
</div>
<div class="page-area" id="metadata-form-page-001-area">
<div class="question-row">
<div class="question-label-cell mandatory">I have read and understood my obligations:</div>
<div class="question-input-cell">
<div class="validation-message"></div>
<label><input type="radio" value="Yes" name="metadata-form-908272-question-1">
<span>Yes</span></label>
<label><input type="radio" value="No" name="metadata-form-908272-question-1">
<span>No</span></label>
</div>
</div>
<div class="question-row">
<div class="question-label-cell">Please state all sources for the information provided:</div>
<div class="question-input-cell">
<div class="validation-message"></div>
<div class="formatted-editor">
<div class="editor-area" contenteditable="true">
<p>​</p>
</div>
</div>
</div>
</div>
</div>
</fieldset>

Update: Security Alert!
Thanks for reminding from #JaredSmith in comment, the method provided here
really has security issue. It's not proper to apply it if the library is not from your internal.
To learn more about the issue, you could look into the link of dangerouslysetinnerhtml I referred below.
Here is indeed a tricky way to achieve your goal. By the information you provided in comment:
... I call theExternalLibrary.getFormFragment({some_data}) ...
cause that DocumentFragments only in memory, maybe as you know, we need to append the fragment to a real DOM element first, so let's just create a root element for appending:
let rootElement = document.createElement("div");
let frag = theExternalLibrary.getFormFragment({some_data});
rootElement.appendChild(frag);
Now we have a pure JavaScript elements DOM tree here. In order to convert it to React elements, here is the way which involves a method that react provides: dangerouslysetinnerhtml
You could see that this method is not encouraged to use by its scary name.
render() {
let rootElement = document.createElement("div");
let frag = theExternalLibrary.getFormFragment({some_data});
rootElement.appendChild(frag);
// rootElement.innerHTML is in string type.
return <div dangerouslySetInnerHTML={{ __html: rootElement.innerHTML }} />;
}
Live example:

I took a crack at this myself, as DOMPurify and the upcoming Sanitiser API work best when returning DocumentFragments:
function getDocumentFragment(text) {
const f = document.createDocumentFragment();
const p = document.createElement("p");
p.textContent = text;
f.appendChild(p);
return f;
}
class FragmentRenderer extends React.Component {
constructor(props) {
super(props);
this.setRef = this.setRef.bind(this);
}
setRef(ref) {
this.ref = ref;
}
componentDidMount() {
this.appendFragment();
}
componentDidUpdate(prevProps) {
if (prevProps.text != this.props.text) {
this.appendFragment();
}
}
appendFragment() {
if (!this.ref) {
return;
}
while (this.ref.firstChild) {
this.ref.removeChild(this.ref.firstChild);
}
this.ref.appendChild(getDocumentFragment(this.props.text));
}
render() {
return React.createElement("div", {
ref: this.setRef
});
}
}
ReactDOM.render(React.createElement(FragmentRenderer, {
text: "Just like this"
}), document.getElementById("app"));
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.6.3/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.6.3/umd/react-dom.production.min.js"></script>
<div id="app"></div>
So now you're not casting to a string and using dangerouslySetInnerHTML, which can in extreme cases lead to the elements you write being different to the elements in the original fragment, due to parsing issues. However, you do still need to trust whereever this fragment came from - it cannot come from a user-controlled source. DOMPurify or the Sanitizer API will be your best friends here.

How to add a <br> tag in reactjs between two strings?

I am using react. I want to add a line break <br> between strings
'No results' and 'Please try another search term.'.
I have tried 'No results.<br>Please try another search term.'
but it does not work, I need to add the <br> in the html.
Any ideas how to solve it?
render() {
let data = this.props.data;
let isLoading = this.props.isLoading;
let isDataEmpty = Object.entries(data).length === 0;
let movieList = isLoading ? <Loader /> : isDataEmpty ? 'No results. Please try another search term.' :
Object.entries(data).map((movie, index) => <MovieTile key={index} {...movie[1]} />);
return (
<div className='movieList'>{movieList}</div>
);
}

You should use JSX instead of string:
<div>No results.<br />Please try another search term.</div>
Because each jsx should have 1 wrapper I added a <div> wrapper for the string.
Here it is in your code:
render() {
let data = this.props.data;
let isLoading = this.props.isLoading;
let isDataEmpty = Object.entries(data).length === 0;
let movieList = isLoading ? <Loader /> : isDataEmpty ? <div>No results.<br />Please try another search term.</div> :
Object.entries(data).map((movie, index) => <MovieTile key={index} {...movie[1]} />);
return (
<div className='movieList'>{movieList}</div>
);
}

You can use CSS white-space to solve the problem.
React Component
render() {
message = `No results. \n Please try another search term.`;
return (
<div className='new-line'>{message}</div>
);
}
CSS
.new-line {
white-space: pre-line;
}
OUTPUT
No results.
Please try another search term.

break text to line:
render() {
...
<div>
{this.props.data.split('\n').map( (it, i) => <div key={'x'+i}>{it}</div> )}
</div>
...

Some HTML elements such as <img> and <input> use only one tag. Such tags that belong to a single-tag element aren't an opening tag nor a closing tag. Those are self-closing tags.
In JSX, one has to include the slash. So, remove <br> and try <br />

Here is how I got around this. Let message be the prop/variable that has the string containing line breaks to be displayed in HTML as follows:
message = 'No results.<br>Please try another search term.';
<div>
{message}
</div>
To make this work, we need to use \n instead of break tag <br> and set the following css on the wrapper element of this message as follows:
message = 'No results.\nPlease try another search term.';
<div className="msg-wrapper">
{message}
</div>
CSS:
.msg-wrapper {
white-space: pre-wrap;
}
OUTPUT:
No results.
Please try another search term.

If you don't want put the string inside a <div> you could use <> to do it.
Like this:
var text = <>This is a text in the first line;<br />this is a text in a second line</>;

Just split text by /n, I do this in this way:
<div>
{text.split('\n').map((item, i) => <p key={i}>{item}</p>)}
</div>

Try with span
return (
<div className='movieList'><span>{movieList}</span></div>
);

If you are like in my situation and you don't want to add css, you can do that :
render () {
...
return (
...
<Typography component="p">
...
{(contact.lastname)?<div>Hello {contact.firstname} {contact.lastname}</div>:''}
...
</Typography>
...
);
}

using ` worked for me however i am not sure if it is the exact solution to the problem :
import React from 'react';
import ReactDOM from 'react-dom';
let element = (
<div>
<h1> Hello world</h1>
This is just a sentence <br></br>
But This line should not be in the same previous line. <br></br>
The above content proves its working. <br></br>
npm v6.14.6 | react : {React.version}
</div>
);
ReactDOM.render(element,document.getElementById("html-element-id"))

You can add a span tag and add block as a class.
Pomodoro Technique Timer <span className="block">with Bla</span>

The simplest thing which I did is by creating a component.
const EmptySpace = ({ spaceCount = 0 }) => {
return (
<>
{Array.from({ length: spaceCount }, (item, index) => {
return <br key={index} />;
})}
</>
);
};
export default EmptySpace;
<EmptySpace spaceCount={1} />
In your case you could do something like this:
const msg = (
<p>
No results <EmptySpace spaceCount={2} />
Please try another search term.
</p>
);