Develop Reference

Alternative to document in next.js

I'm still new to learning next.js, but the problem is, I don't understand. How do we call an element from the written html because I want to do like the code written below?
HTML
<div class="container_title">
<div class="main_title">
<h1> Title <span>( Global )</span></h1>
<div class="button_main_title">
<button class="Tap_1 button" >Tap_1 </button>
<button class="Tap_2 button">Tap_2</button>
<button class="Tap_3 button">Tap_3</button>
<button class="Tap_4 button">Tap_4</button>
<button class="Tap_5 button">Tap_5</button>
</div>
</div>
</div>
javascript
const main_title = document.querySelector(".main_title");
const button_main_title = document.querySelectorAll(".main_title button");
(() => {
main_title.addEventListener('click', event => {
if(event.target.classList.contains("button")){
for(i=0;i<button_main_title.length;i++) button_main_title[i].classList.remove("active");
event.target.classList.add("active")
}
})
})();
const Firsr_BTN = document.querySelector(".button_main_title .button:first-child");
Firsr_BTN.click();

NextJS is a framework which is based on React, which is based on Javascript. However, the only way that I know to select an element is to use a React hook called useRef. Let me give you an example.
import React, { useRef } from 'react'
const YourComponent = () => {
const myHeading = useRef()
console.log('heading', myHeading)
return (
<div>
<h1 ref={myHeading}>Heading</h1>
</div>
)
}
Now you have your h1 as myHeading and you can modify it the way you want. Always check your console for what's the element object looks like and how to edit it.

How to store the return value of a function inside a variable in reactJS

my code:
import "./styles.css";
export default function App() {
getUserValue = (e) => {
let value = e.target.value;
console.log(value)
return value
}
let userInputValue = getUserValue
return (
<div>
<div>
<h4>Sign Up</h4>
</div>
<div>
<div>
<p>Username</p>
<input onChange = {getUserValue}/>
</div>
<div >
<p>Password</p>
<input/>
</div>
</div>
<div>
<button onClick = {console.log(userInputValue)}>Submit</button>
</div>
<div>
<button>
Close
</button>
</div>
</div>
);
}
code sandbox: https://codesandbox.io/s/dazzling-sea-my5qm?file=/src/App.js:0-720
I'm trying to store the returned value of "getUserValue" function to "userInputValue" variable so I can log the input the user made and use it in different functions. I can't get it to work though, when I console log the variable hoping to get the returned result after I made an input I don't get anything, as if the button doesn't work.

I'm trying to store the returned value of "getUserValue" function to "userInputValue" variable so I can log the input the user made and use it in different functions.
You'd do that by making the input state in your component. In a function component like yours, that means using the useState hook (or various libraries like Redux that have alternative ways of doing it).
Here's a simple example, but you can find lots of more complex ones by searching:
const { useState } = React;
function Example() {
// Call the hook to get the current value and to
// get a setter function to change it. The default
// value ("" in this example) is only used the first
// time you call the hook in this component's lifecycle
const [userInput, setUserInput] = useState("");
// Handle changes in the input by setting state.
// Note that this function is recreated every time your
// component function is called to update. That's mostly
// fine, but there are times you might want to optimize
// that.
const onChange = (event) => {
setUserInput(event.currentTarget.value);
};
// Handle clicks on the button that show' the current input.
const onClick = () => {
console.log(`The current userInput is "${userInput}"`);
};
// Return the rendering information for React
return <div>
{/* Provide the value and hook the "change" (really "input") event */}
<input type="text" value={userInput} onChange={onChange} />
<input type="button" onClick={onClick} value="Show Current" />
</div>;
}
ReactDOM.render(<Example />, document.getElementById("root"));
<div id="root"></div>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/17.0.2/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/17.0.2/umd/react-dom.production.min.js"></script>

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>
}

Parse nested HTML that's within a string in React?

I'm building a type ahead feature in React.
I have wrapper component that has an array of objects, and it renders item; which's a stateless component.
So, suppose I have const name= 'Hasan'. Which gets parsed to >> const parsedName = Ha<span>san</span>; assuming the term to search for is san.
I have tried dangerouslySetInnerHTML={{ __html: parsedName }} attribute on the parent element, but it didn't work.
With plain html this would be: el.innerHTML = parsedName
The goal is to style the span as desired. Any ideas?

class Test extends React.Component {
render() {
const name = 'san';
const parsedName = name.replace(new RegExp('san', 'ig'), '<span>span</span>');
return (
<div dangerouslySetInnerHTML={{__html: parsedName}}/>
);
}
}
ReactDOM.render(
<Test/>,
document.getElementById('container')
);
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react-dom.min.js"></script>
<div id="container">
</div>
Without code its hard to tell what's wrong. I have created a working snippet here that might help you debug your issue.
Updated the example based on the comment.

Passing html element value to composeWithTracker in React

This Meteor code uses React. When user fills in an input box with id myVal, click a button. The input box value gets sent to the server via a method, the server updates the collection vehicles.
It then needs to take that input from user and use that as query to collection.findOne in myfile.jsx. It failed to pass the user input myVal from html input element.
How can it be done? Thanks
// -------------------- myfile.jsx -------------------
const renderWhenData = ( cars ) => {
if ( cars ) {
return <span>{ cars.description }</span>;
}
};
const Info = ( { cars } ) => (
<p>{ renderWhenData( cars ) }</p>
);
const composer = (props, onData) => {
const subscription = Meteor.subscribe('vehicles');
if (subscription.ready()) {
let myVal = document.getElementById('myVal').value;
console.log(myVal); // <------------------ nothing is printed out
const cars = Vehicles.findOne({name: myVal});
onData(null, {cars});
}
};
const Container = composeWithTracker(composer)(Info);
ReactDOM.render(<Container />, document.getElementById('react-info'));
// --------------------- events.js -----------------------
document.getElementById('startButton').addEventListener('click', () => {
const myVal = document.getElementById('myVal').value;
Meteor.call('startInfo', myVal); // <---------- updates server collection
});
<!--main.html-->
<head>
</head>
<body>
<form action="submit">
<input type="text" id="myVal">
<div id="react-info"></div>
</form>
<footer>
<button id="startButton">START</button>
</footer>
</body>

The question is a bit academic. There are better ways to handle this in React. But, since you are using Meteor, this can be done with some Tracker operations.
First define a tracker dependency:
export const textboxDep = new Tracker.Dependency;
Whenever the textbox value changes, trigger the changed event.
textboxDep.changed();
Within the composer, use
textboxDep.depend();
If the composer is written well, when the tracker dependency is invalidated, the whole functional container component runs again. And you should see the value of the textbox there.
Right now, when the value of the textbox is changed, since it is not reactive, the container does not re-render itself.