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');

can't append h1 element to parent div in React?

i'm creating a simple react website that's supposed to do some calculations and find out Joules of my input values after the calculations...right now the input values are already preset but i will remove the value="" from my <input> later.
here is the .JSX component file that's the issue...one of the components.
import React, { Component } from 'react';
import Atom_icon from './cartridges.png';
class Joule_calc extends Component {
render(){
return (
<div className='Joule_div'>
<h3 style={{color:"white", textAlign:"center"}}>JOULE CALCULATOR</h3>
<label className='lab1'>WEIGHT=/GRAMS</label><br></br>
<input className='weight_inp' type='text' value="2" />
<label className='lab2'>SPEED=M/S</label><br></br>
<input className='speed_inp' type='text' value="5" />
<button className='count_button' onClick={this.Create_response}>CALCULATE</button>
<h1 className='Result_joule'></h1>
</div>
)
}
Create_response(){
console.log("creating response...")
let sum = document.createElement("h1")
sum.className = 'Result_joule'
sum.textContent = "678"
let div_panel = document.getElementsByClassName("Joule_div")
div_panel.append('Result_joule')
}
Returned_values(){
let weight_val = document.getElementsByClassName("weight_inp")[0].value;
let speed_val = document.getElementsByClassName("speed_inp")[0].value;
let final_calculation = weight_val * speed_val
return final_calculation
}
}
export default Joule_calc
so when i run my code i get
Uncaught TypeError: div_panel.append is not a function
at Create_response (Joule_calc_window.jsx:31:1)
i don't get why i can't append my new element to the div. it says it's not a function so what's the solution then? i'm new to React and web so probably it's just a noobie thing.
also i tried directly creating a h1 inside the 'Joule_div' like this.
<h1 className='Result_joule'>{"((try returning here from one of these methods))"}</h1>
but that of course failed as well. So would appreciate some help to get what's going on. i'm trying to add a number after the button click that's in h1 and in future going to be a returned number after calculating together the input values in a method.i imagine that something like
MyMethod(){
value = values calculated
return value
}
and later grab it with this.MyMethod
example
<h1>{this.MyMethod}</h1>
this is a example that of course didn't work otherwise i wouldn't be here but at least gives you a clue on what i'm trying to do.
Thank you.

You don't leverage the full power of react. You can write UI with only js world thanks to JSX. State changes triggering UI update.
I may miss some specificaiton, but fundamental code goes like the below. You should start with function component.
// Function component
const Joule_calc = () =>{
// React hooks, useState
const [weight, setWeight] = useState(0)
const [speed, setSpeed] = useState(0)
const [result,setResult] = useState(0)
const handleCalculate = () =>{
setResult(weight*speed)
}
return (
<div className="Joule_div">
<h3 style={{ color: 'white', textAlign: 'center' }}>JOULE CALCULATOR</h3>
<label className="lab1">WEIGHT=/GRAMS</label>
<br></br>
<input className="weight_inp" type="text" value={weight} onChange={(e)=>setWeight(parseFloat(e.target.value))} />
<label className="lab2">SPEED=M/S</label>
<br></br>
<input className="speed_inp" type="text" value={speed} onChange={(e)=>setSpeed(parseFloat(e.target.value))} />
<button className="count_button" onClick={handleCalculate}>
CALCULATE
</button>
<h1 className='Result_joule'>{result}</h1>
</div>
)
}
export default Joule_calc;

div_panel is an collection of array which contains the classname ["Joule_div"]. so first access that value by using indexing . and you should append a node only and your node is "sum" not 'Result_joule' and you should not use textcontent attribute because you will be gonna definitely change the value of your result as user's input value
Create_response(){
console.log("creating response...")
let sum = document.createElement("h1")
sum.className = 'Result_joule'
//sum.textContent = "678"
let div_panel = document.getElementsByClassName("Joule_div")
div_panel[0].append('sum')
}
if any problem persists , comment below

Cannot add our own react element onclick

I am working on a tasklist page. The main page has a form in which the user would add the task and click on the add task button and the corresponding task would be appended to the "todo-task" div. I am using my own created react element (Do laundry is just for example) which returns a checkbox followed by the text passed as prop. In the following code I am trying to append at the end of our todo-task div but it is showing me some error. Is my approach right? If not what approach should I take?
import React,{useState} from 'react'
import './Tasklist.css'
import Button from 'react-bootstrap/Button';
import AddBoxIcon from '#material-ui/icons/AddBox';
import Checkbox from '#material-ui/core/Checkbox';
import Task from './Task.js';
function Tasklist() {
const [task, settask] = useState("")
let pendingTask = document.getElementById('pending-task')
let doneTask = document.getElementById('done-task')
const addTask = (event)=>{
event.preventDefault()
let tmp_text=task.trim()
if(tmp_text==="")return
let task_tmp = document.createElement(<Task text={tmp_text} />);
pendingTask.appendChild(task_tmp);
settask("");
}
const keyDownEvent=(e)=>{
let key=e.key
if(key==='Enter' && !e.shiftKey)addTask(e);
}
return (
<>
<div className="add-task">
<form >
<textarea
type="text"
value={task}
rows={1}
placeholder="Add Task"
onChange={(e)=>settask(e.target.value)}
onKeyDown={keyDownEvent}
/>
<Button variant="outline-primary" onClick={addTask}>
<AddBoxIcon /> Add Task
</Button>
</form>
</div>
<div className="todo-task" id="pending-task">
</div>
<Task text="Enjjoyyyy!!!" />
<hr />
<div className="done-task" id = "done-task">
<ul id="done-task-list">
</ul>
</div>
</>
)
}
export default Tasklist

You're going about this in a fundamentally incorrect way, so it's not a quick fix. Now is the time to take a big step back and start over on your component.
What you're currently trying to do is modify the DOM directly. Don't do that in React. What you should instead be doing is maintaining state.
Instead of trying to directly create an element and add it to the DOM, create a record and update state with that record. This is an entirely separate task than rendering the DOM. The actual rendering is done based on that current state.
Currently in your state you have "a task". But you're trying to build functionality to add more tasks. So really your state should have a list of tasks, and you can add to that list. (Which can be in addition to the single task, of course. You can use useState as many times as you like.)
For example, consider state like this:
const [tasks, setTasks] = useState([]);
Then add a task in your button click handler:
const addTask = (event)=>{
event.preventDefault();
let tmp_text=task.trim();
if(tmp_text==="") return;
setTasks([...tasks, tmp_task]); // <--- here
settask("");
}
This keeps a running array of the tasks being stored.
Then in the rendering, you would .map over those tasks to show them:
<div className="todo-task" id="pending-task">
{tasks.map((t, i) => (
<Task key={i} text={t} />
))}
</div>

How do I insert icon in from createElement

I am currently using Material-UI-icon and need to create the icon by in javascript.
Is there a way where I can do this?
import ThumbUpIcon from '#material-ui/icons/ThumbUp';
var thumbsup = document.createElement(ThumbUpIcon);
Thanks!

Instead of document.createElement I would use as a variable or like <ThumbUpIcon />.
You can try the following:
import ThumbUpIcon from '#material-ui/icons/ThumbUp';
var thumbsup = <ThumbUpIcon />;
Then in the return part:
const YourComponent = () => {
return (
<div>
<h1> First option: </h1>
{thumbsup}
<h1> Second option: </h1>
<ThumbUpIcon />
</div>
)
}
Additionally I would suggest to read: Creating React Elements
I hope that helps!

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>
}