Develop Reference

How to assign a classname to particular division after map in React js?

I am mapping data inside a div, all i need a border to div of "lab_add_to_cart_samp1" classname after clicking that division. I am confused how to make a division show active onclick even after mapping the data, there is an array of allabtest from API call
<div className="lab_add_to_cart_samp">
{
allabtest.map((item, index) => {
return <div className="lab_add_to_cart_samp1" key={index}>
<div className="lab_add_to_cart_samp_img1">
<img src={REACT_APP_BASE_URL+"lab-test/download/"+item.id} />
</div>
<div className="lab_add_to_cart_test_desc">
<p id="labtest_desc_txt1">{item.name}</p>
<p id="labtest_desc_txt2">What it include :</p>
<div className="labtest_desc1">
<div className="labtest_desc_detail">
<ul>
<li>Platate</li>
<li>CBC</li>
<li>HB</li>
</ul>
</div>
<div>
<ul id="lab_test_detail">
<li>PCV</li>
<li>WBC/TLC</li>
<li>WBC/TLC</li>
</ul>
</div>
<div>
<ul id="lab_test_detail">
<li>DLC</li>
<li>RBC</li>
<li>ESR</li>
</ul>
</div>
<div>
<ul id="lab_test_detail">
<li>Platelets</li>
<li>Reticilocytes</li>
<li>Blood Grouping Rh type</li>
</ul>
</div>
</div>
</div>
<div className="lab_add_to_cart_price">
<p>Rs. {item.price}</p>
<div className="lab_add_to_cart_atc">
<button onClick={()=>addtocart(item)}>
<p>Add to Cart</p>
</button>
</div>
</div>
</div>
})
}
</div>

If you want to set active for multiple divs at the same time you can do it like this
const allabtest = [
{id: 'one', name: 'one'},
{id: 'two', name: 'two'},
{id: 'three', name: 'three'},
]
function App() {
const [activeCart, setActiveCart] = useState({});
return (
<div className="lab_add_to_cart_samp">
{allabtest.map((item, index) => {
return (
<div
className={
activeCart[item.id] === true
? "lab_add_to_cart_samp1 active"
: "lab_add_to_cart_samp1"
}
onClick={() =>
setActiveCart({
...activeCart,
[item.id]: !Boolean(activeCart[item.id])
})
}
key={item.id}
>
<div>{item.name}</div>
</div>
);
})}
</div>
);
}
If you want to track only one div then
function App() {
const [activeCart, setActiveCart] = useState();
return (
<div className="lab_add_to_cart_samp">
{allabtest.map((item, index) => {
return (
<div
className={
activeCart === item.id
? "lab_add_to_cart_samp1 active"
: "lab_add_to_cart_samp1"
}
onClick={() => setActiveCart(item.id)}
key={item.id}
>
{/* Rest of your stuffs */}
</div>
);
})}
</div>
);
}

How Can I change the property of components of React?

I am new to React and recently started working on it. I know that we cannot change the components properties using the props.
I want to know how can we change the properties of Component?
Below is my code:
Courses.jsx
function Courses(){
return (
<div className="courses">
<h1>Ongoing Courses</h1>
<div className="row">
{CourseData.map((value,index)=>{
return (
<div className="col-md-3">
<Card title={value.title} completed={value.completed} content={value.content} value="Resume !" key={index} id={index} />
</div>
);
})}
</div>
</div>
);
}
Here above i am having a Array of Data named as courseData, I am mapping it on a Card component.
Card.jsx:
function Card(props){
function handleClick(){
}
return (
<div className="card">
<div className="card-body">
<h2 className="card-title">{props.title}</h2>
{props.content}
<br/>
<button className="btn btn-danger" > {props.value}</button>
</div>
</div>
);
}
the CourseData has following properties :
courseData : [{
key,
title,
completed
content}]
I simply want that when ever the button present is card gets clicked then the completed attribute of courseData changed to some different value that is passed through the props .
I have tried a lot but not able to do .
Any help regarding this will be helpful for me .
courseData.jsx:
const notes = [{
key: 1,
title: "some Text",
completed:false,
content: "some Text"
},
{
key: 2,
title: "some Text",
completed:false,
content: "some Text"
}]
export default notes;

Add CourseData to the state of the Courses component. Then add a method to adjust the data there. Pass the method throught props that will be called when clicking button in the Card component:
function Courses() {
const [courseData, setCourseData] = useState(CourseData);
const updateCourseData = (index) => {
courseData.splice(index, 1);
setCourseData(courseData);
}
return (
<div className="courses">
<h1>Ongoing Courses</h1>
<div className="row">
{courseData.map((value,index)=>{
return (
<div className="col-md-3">
<Card title={value.title} updateCourseData={updateCourseData} completed={value.completed} content={value.content} value="Resume !" key={index} id={index} />
</div>
);
})}
</div>
</div>
);
}
in the Card.jsx:
<button onClick={() => props.updateCourseData(props.id)} className="btn btn-danger" > {props.value}</button>

function Courses(){
const [coursesData, setCoursesData] = useState(CourseData)
return (
<div className="courses">
<h1>Ongoing Courses</h1>
<div className="row">
{coursesData.map((value,index)=>{
return (
<div className="col-md-3">
<Card coursesData={coursesData} setCoursesData={setCoursesData} title={value.title} completed={value.completed} content={value.content} value="Resume !" key={index} id={index} />
</div>
);
})}
</div>
</div>
);
function Card({id,title,value,content,coursesData,setCoursesData }){
function handleClick(e){
e.preventDefault()
setCoursesData(coursesData => {
const data = coursesData
data.splice(id,1,{
title: title,
completed: value,
content: content,
key: id
})
return data
})
}
return (
<div className="card">
<div className="card-body">
<h2 className="card-title">{title}</h2>
{content}
<br/>
<button onClick={handleClick} className="btn btn-danger">{value}</button>
</div>
</div>
);

Cards inside the grid-container: each child in a list should have a unique "key" prop

What I`m doing wrong?It also says: "Check the render method of Card" , which is here:
<div className="grid-container">
{pokemonData.map((pokemon, i) => {
console.log(pokemon.id) // unique numbers are here
return <Card key={pokemon.id} pokemon={pokemon} />
})}
</div>
Card component itself:
function Card({ pokemon }) {
return (
<div className="card">
<div className="card__image">
<img src={pokemon.sprites.front_default} alt="Pokemon" />
</div>
<div className="card__name">
{pokemon.name}
</div>
<div className="card__types">
{
pokemon.types.map(type => {
return (
<div className="card__type" style={{backgroundColor: typeColors[type.type.name]}}>
{type.type.name}
</div>
)
})
}
</div>
<div className="card__info">
<div className="card__data card__data--weight">
<p className="title">Weight:</p>
<p>{pokemon.weight}</p>
</div>
<div className="card__data card__data--height">
<p className="title">Height:</p>
<p>{pokemon.height}</p>
</div>
<div className="card__data card__data--ability">
<p className="title">Abilities:</p>
{/* {console.log(pokemon.abilities)} Temporary for dev puprose */}
{pokemon.abilities.map(ability => <p>{ability.ability.name}</p>
)}
</div>
</div>
</div>
);
}
export default Card;

You can use the index of the array may be your data is having some kind of duplicate. It is recommended that you pass a key prop whenever you are returning a list.
<div className="grid-container">
{pokemonData.map((pokemon, i) => {
console.log(pokemon.id) // unique numbers are here
return <Card key={i} pokemon={pokemon} />
})}
</div>
Equally, check this segment of card components.
{
pokemon.types.map((type,i) => {
return (
<div key={i} className="card__type" style={{backgroundColor:
typeColors[type.type.name]}}>
{type.type.name}
/div>
)
})
}
And
<div className="card__data card__data--ability">
<p className="title">Abilities:</p>
{/* {console.log(pokemon.abilities)} }
{pokemon.abilities.map((ability, i) => <p key={i}>{ability.ability.name}
</p>
)}
</div>

Previous answer will solve your problem. However, for your info, I would also like to add here.
For React a key attribute is like an identity of a node/element/tag which helps React to identify each item in the list and apply reconciliation correctlyon each item. Without a key React will render your component but may cause issue when you re-order your list.
React recommends to use id of the data instead of index number. However, if your list does not re-orders/ sorts or do not have id then you can use index.
You can read more here:
https://reactjs.org/docs/lists-and-keys.html

Change this:
<div className="card__types">
{
pokemon.types.map(type => {
return (
<div className="card__type"
style={{backgroundColor:typeColors[type.type.name]}}
>
{type.type.name}
</div>
)
})
}
</div>
to:
<div className="card__types">
{
pokemon.types.map((type, key) => {
return (
<div key={key} className="card__type"
style={{backgroundColor:typeColors[type.type.name]}}
>
{type.type.name}
</div>
)
})
}
</div>
and:
{pokemon.abilities.map(ability => <p>{ability.ability.name}</p>
to:
{pokemon.abilities.map((ability,key) => <p key={key} >{ability.ability.name}</p>

Conditionally adding a row after 3 elements: ReactJS

I want to render several row containing three columns each. The columns have just a Card. The way I thought I could do this is to map through the elements and create a row when the index modulus is 0 and close that row when it's the third column of the row. I've tried with if-else statements and with ternary operators. But I keep getting syntax errors.
render(){
var { isLoaded, items } = this.state;
if(!isLoaded) {
return (<div> Fetching items </div>);
}
else {
var results = items.results;
return (
<div className="App">
<div className ="container">
{ result.map ((result, i) => {
return(
{i%3===0 ?
<div className ="row mt-4">
<div key ={i} className="col-md-4">
<Card result={result}></Card>
</div>
:
<div key ={i} className="col-md-4">
<Card result={result}></Card>
</div>);
}
{i%3===1 ?
</div>
:null}
})}
</div>
</div>
);
}
}
With this piece of code I'm getting an error in this line
{i%3===0 ?
How can I solve this?

Because, you have a unclosed <div> tag which is invalid JSX, also { in return means an object not dynamic content.
Don't forget we write JSX, not html. Each tag needs to be closed properly, because it will get converted into React.createElement(component/html tag, props, children).
To solve the problem, first prepare the array and after 3 items, just push the elements in row arrays, like this:
renderRows() {
let results = items.results;
let finalArr = [], columns = [];
result.forEach ((result, i) => {
// prepare the array
columns.push(
<div key ={i} className="col-md-4">
<Card result={result}></Card>
</div>
);
// after three items add a new row
if((i+1) % 3 === 0) {
finalArr.push(<div className ="row mt-4">{columns}</div>);
columns = [];
}
});
return finalArr;
}
render(){
var { isLoaded, items } = this.state;
if(!isLoaded) {
return (<div> Fetching items </div>);
} else {
return (
<div className="App">
<div className ="container">
{this.renderRows()}
</div>
</div>
);
}
}

You are getting the error, because you are not rendering a valid element each time - it is missing a closing tag when "i%3===0" resolves to true.
<div className ="row mt-4">
<div key ={i} className="col-md-4">
<Card result={result}></Card>
</div>
</div> // <-- this one
Also, you could just render all the cards in that one container and set the style of the card accordingly to be the width of a third of the parent container.
<div className="container">
{result.map((result, i) => {
return (
<div key={i} className="col-md-4"> // add styles for width 30%
<Card result={result} />
</div>
);
})}
</div>
And one other idea is that instead of feeding data like [1,2,3,4,5], you could reduce the array to buckets of other arrays like [[1,2,3], [4,5,6]] and render those.
<div className="container">
{result.map((row, i) => (
<div key={i} className="row mt-4">
{row.map((col, i) => (
<div key={i} className="col-md-4">
<Card result={col} />
</div>
))}
</div>
))}
</div>
P.s. don't use the index for the element key. Use something unique, like the value of the card or an id.

You are simply missing some closing brackets.
Try this,
<div className ="row mt-4">
{ result.map ((result, i) => {
return(
<React.Fragment>
{(i%3===0) ?
<div key ={i} className="col-md-4">
<Card result={result}></Card>
</div>
:
<div key ={i} className="col-md-4">
<Card result={result}></Card>
</div>
}
</React.Fragment>
)
})}
</div>
As per your code,
{ result.map ((result, i) => {
return(
{i%3===0 ?
<div className ="row mt-4">
<div key ={i} className="col-md-4">
<Card result={result}></Card>
</div>
:
<div key ={i} className="col-md-4">
<Card result={result}></Card>
</div>); //You have added `);` which is cause of error. this means you are returning this much part only.

Here's how you can fix it:
render() {
const { isLoaded, items } = this.state;
if (!isLoaded) {
return (<div> Fetching items </div>);
}
const results = items.results;
return (
<div className="App">
<div className="container">
{results.map((result, i) => (
<React.Fragment>
{(i + 1) % 4 === 0 ?
(<div className="row mt-4" key={`row-${i}`}>
<div key={i} className="col-md-4">
<Card result={result} />
</div>
</div>) :
(<div key={i} className="col-md-4">
<Card result={result} />
</div>)}
{i % 3 === 1 ? <div /> : null }
</React.Fragment>
))}
</div>
</div>
);
}
I strongly suggest you to use ESLint or linter to find and fix these errors then and there. Take a look at: https://medium.com/#RossWhitehouse/setting-up-eslint-in-react-c20015ef35f7. Eslint will help you with better indentation, matching brackets, best practices and much more. Once you have set eslint, you can sort these out yourself.
Edit:
Grouping items into four and putting them under one row:
class Application extends React.Component {
constructor(props) {
super(props);
this.state = {
loading: false,
isLoaded: true,
items: {
results: ["1", "2", "3", "4", "5", "6", "7", "8"]
}
};
}
render() {
const { isLoaded, items } = this.state;
if (!isLoaded) {
return (<div> Fetching items </div>);
}
const results = items.results;
// Group them into sets of 4.
const grouped = results.reduce((acc, post, ind) => {
var index = parseInt(ind / 4);
acc[index]= acc[index] || [];
acc[index].push(<div key={`colmn-${index}`} className="col-md-4">{results[ind]}</div>);
return acc;
}, []);
return (
<div className="App">
<div className="container">
{grouped.map((row, i) => {
return <div className="row mt-4" key={`row-${i}`}>{row}</div>})}
</div>
</div>
);
}
}
ReactDOM.render(<Application />, document.getElementById("retrospect-app"));
<link href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/4.3.1/css/bootstrap.css" rel="stylesheet"/>
<div id="retrospect-app"></div>
<script crossorigin src="https://unpkg.com/react#16/umd/react.development.js"></script>
<script crossorigin src="https://unpkg.com/react-dom#16/umd/react-dom.development.js"></script>
<script src="https://unpkg.com/babel-standalone#6/babel.min.js"></script>

React Component populate Item component props from Json data

I have a React component which list items from the Item component.
Below you can see how it looks.
const ListHolder = () => (
<div>
<div className="panel">
<div className="panel-heading">
<h3 className="panel-title">List Title</h3>
</div>
<div className="panel-body">
<Item
title="A Title"
desc="Desc 1."
/>
<Item
title="Another Title"
desc="Desc 2."
/>
<Item
title="Some of title"
desc="Desc 3."
/>
</div>
</div>
</div>
);
export default ListHolder;
Item components are currently hardcoded.
How can I populate / insert the data from some Json data?

If you pass your items data as props of your component, you could do something like:
const ListHolder = ({items}) => (
<div>
<div className="panel">
<div className="panel-heading">
<h3 className="panel-title">List Title</h3>
</div>
<div className="panel-body">
{ items.map((item) => <Item title={item.title} desc={item.desc} />)}
</div>
</div>
</div>
);
~ EDIT after first comment ~
That is if you can use so called
Otherwise the "usual" way can look something like:
class ListHolder extends React.Component {
render() {
const items = [{ "title": "title", "desc": "some desc" }, { "title": "title2", "desc": "some other desc" }];
return (
<div>
<div className="panel">
<div className="panel-heading">
<h3 className="panel-title">List Title</h3>
</div>
<div className="panel-body">
{ items.map((item) => <Item title={item.title} desc={item.desc} /> )}
</div>
</div>
</div>
);
}
}