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Wrong rendering when using map to render from an array in React

In this issue, I have an array of objects like:
const sampleCards = [
{userName:'user1',avatarURL:'../avatar/role11.jpg',mainPageURL:'/',isFollowed:true},
{userName:'user2',avatarURL:'../avatar/role12.jpg',mainPageURL:'/',isFollowed:true},
{userName:'user3',avatarURL:'../avatar/role13.jpg',mainPageURL:'/',isFollowed:false},
];
then I used map() to render this array:
export default function SearchBar(){
return (
<div className='searchBar'>
{sampleCards.map((result)=>{
return (
<SearchResultCard result={result}/>
);
})}
</div>
);
}
A SearchResultCard component be like:
export default function SearchResultCard(result){
const [isFollowed,setIsFollowed] = useState(result.isFollowed);
const handleFollowingClicked = ()=>{
setIsFollowed(false);
};
const handleFollowClicked=()=>{
setIsFollowed(true);
};
useEffect(()=>{console.log(result.userName)});
return (
<div className="search-result-card">
<Link to={result.mainPageURL}>
<div className="search-result-card-left">
<img src={result.avatarURL} alt={result.userName} className="search-result-img"/>
<p>{result.userName}</p>
</div>
</Link>
{isFollowed ? (
<button className="following-button" onClick={handleFollowingClicked}>Following</button>
):(
<button className="follow-button" onClick={handleFollowClicked}>Follow</button>
)}
</div>
);
}
The problem is that values in result seem not been passed to so it just ends with a 'Follow' button while other elements are not rendered

The parameter in SearchResultCard is the entire props object. This has a property called result. You need to destructure to get the result prop:
function SearchResultCard({ result }){ ... }
Here's a snippet:
const {useState} = React;
const sampleCards = [
{ userName:'user1', isFollowed:true },
{ userName:'user2', isFollowed:true },
{ userName:'user3', isFollowed:false },
];
function SearchResultCard({ result }){
const [isFollowed,setIsFollowed] = useState(result.isFollowed);
const handleFollowingClicked = _ => setIsFollowed(false);
const handleFollowClicked= _ => setIsFollowed(true);
return (
<div className="search-result-card">
{isFollowed
? ( <button onClick={handleFollowingClicked}>Following</button>)
: ( <button onClick={handleFollowClicked}>Follow</button>)
}
</div>
);
}
function Example(){
return (
<div className='searchBar'>
{sampleCards.map((result)=>{
return (
<SearchResultCard key={result.userName} result={result}/>
);
})}
</div>
);
}
// Render it
ReactDOM.createRoot(
document.getElementById("root")
).render(
<Example />
);
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/18.2.0/umd/react.development.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/18.2.0/umd/react-dom.development.js"></script>
<div id="root"></div>

Short circuiting not working in react render div

I want to start multiple components when a variable is true and I am using as follow:
return (
<div className="report">
{conditionalVariable &&
<ComponentA/> &&
<ComponentB/>
}
</div>
)
However, when the variable is true, only component A is getting up but not component B.What is wrong with this ?

I'm surprised you're getting any output. Those conditional components once you've worked out the logic, need to have a parent - either with a fragment, or a div, or something.
You would have seen something similar to this error:
SyntaxError: Inline Babel script: Adjacent JSX elements must be wrapped in an enclosing tag
const { Fragment, useState } = React;
function Example() {
const [ conditional, setConditional ] = useState(false);
function handleClick() {
setConditional(!conditional);
}
return (
<div>
{conditional && (
<Fragment>
<Test text="Bob" />
<Test text="Sue" />
</Fragment>
)}
<button onClick={handleClick}>
Click me
</button>
</div>
);
}
function Test({ text }) {
return <p>{text}</p>;
}
ReactDOM.render(
<Example />,
document.getElementById('react')
);
<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>
<div id="react"></div>

Your curly braces are set rather strange. Try it like this:
return (
<div className="report">
{conditionalVariable &&
<>
<ComponentA />
<ComponentB />
</>
}
</div>
)
This solution uses the short syntax of React.Fragment to group the two components you want to display under the same condition.

React is rendering [Object object] instead of JSX elements inside the array

I have this array of buttons in my React application:
const buttons = [
<Button label='Close' onClick={props.handleClose} />,
<Button label='Save' onClick={props.handleSubmit} />,
<Button label='Reset' onClick={props.handleReset} />
]
But when I render them:
render() {
return (
<div className='buttons'>{buttons.join()}</div>
)
}
I get:
Object object Object object Object object
And I want to get those elements.

There is no need to use .join(). It's enough to just pass an array like that:
render() {
return (
<div className='buttons'>{buttons}</div>
)
}

Why need to use join. There is no need.
const buttons = [
<Button label='Close' onClick={props.handleClose} />,
<Button label='Save' onClick={props.handleSubmit} />,
<Button label='Reset' onClick={props.handleReset} />
]
render() {
return (
<div className='buttons'>{buttons}</div>
)
}

Render an array of Objects in ReactJs

I am trying to go through object properties (Name for this example) and list them within easy loop in function. I have found some pretty awkward way of doing this but it doesn't seem right.
Here is what i got:
const ItemsToSell = [{"Name":"Cup","Price":"99.99"},{"Name":"IPhone","Price":"99.99"},{
"Name":"Pen","Price":"99.99"}]
function ListItem(props) {
return <li>{props.value}</li>;
}
function NumberList(props) {
const a = props.numbers;
return (
<ul>
{a.map((number) =>
<ListItem value={ItemsToSell[number].Name} />
)}
</ul>
);
}
const numbers = [0,1, 2];
ReactDOM.render(
<NumberList numbers={numbers} />,
document.getElementById('root')
);
<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="root"></div>
Is there a better way to do this?
I simply need a loop to go through array of objects, list needed properties and create one of many html nodes.

You can simply map over ItemsToSell array
const ItemsToSell = [{"Name":"Cup","Price":"99.99"},{"Name":"IPhone","Price":"99.99"},{
"Name":"Pen","Price":"99.99"}]
function ListItem(props) {
return <li>{props.value}</li>;
}
function NumberList(props) {
return (
<ul>
{ItemsToSell.map((obj, index) =>
<ListItem key={index} value={obj.Name} />
)}
</ul>
);
}
ReactDOM.render(
<NumberList />,
document.getElementById('root')
);
<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="root"></div>

Why don't you iterate over ItemsToSell array? You don't have to add yet another one.
Note: Include key property while looping the elements, else you will receive an error.
const ItemsToSell = [{"Name":"Cup","Price":"99.99"},{"Name":"IPhone","Price":"99.99"},{
"Name":"Pen","Price":"99.99"}]
function ListItem(props) {
return <li>{props.value}</li>;
}
function NumberList(props) {
return (
<ul>
{ItemsToSell.map((elem, index) =>
<ListItem value={elem.Name} key={index} />
)}
</ul>
);
}
ReactDOM.render(
<NumberList />,
document.getElementById('root')
);
<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="root"></div>

Return multiple React elements in a method without a wrapper element

I'm trying to return multiple React elements from a helper method. I could solve it simply by moving around some code, but I'm wondering if there's a cleaner way to solve it. I have a method that returns part of the render method, and that functions needs to return both a React element and some text. It's clearer through an example:
class Foo extends React.Component {
_renderAuthor() {
if (!this.props.author) {
return null;
}
return [
' by ',
<a href={getAuthorUrl(this.props.author)}>{this.props.author}</a>,
]; // Triggers warning: Each child in an array or iterator should have a unique "key" prop.
render() {
return (
<div>
{this.props.title}
{this._renderAuthor()}
</div>
);
}
}
I know the render method has to return exactly 1 React element. Using a helper method like this would trigger a warning, and fixing the warning (by adding keys) would make the code too convoluted. Is there a clean way to do this without triggering a warning?
Edit:
Another use case:
render() {
return (
<div>
{user
? <h2>{user.name}</h2>
<p>{user.info}</p>
: <p>User not found</p>}
</div>
);
}
Edit 2:
Turns out this isn't possible yet, I wrote about 2 workarounds here: https://www.wptutor.io/web/js/react-multiple-elements-without-wrapper

Support has been added using the Fragment component. This is a first-class component.
So you can now use:
render() {
return (
<React.Fragment>
<ChildA />
<ChildB />
<ChildC />
</React.Fragment>
);
}
For more information visit: https://reactjs.org/blog/2017/11/28/react-v16.2.0-fragment-support.html

The error message tells you exactly how to solve this:
Each child in an array or iterator should have a unique "key" prop.
Instead of this:
return [
' by ',
<a href={getAuthorUrl(this.props.author)}>{this.props.author}</a>,
];
Do this:
return [
<span key="by"> by </span>,
<a key="author" href={getAuthorUrl(this.props.author)}>{this.props.author}</a>,
];
Yes, you need to wrap the text node ("by") in a span in order to give it a key. Such are the breaks. As you can see, I've just given each element a static key, since there's nothing dynamic about them. You could just as well use key="1" and key="2" if you wanted.
Alternatively, you could do this:
return <span> by <a href={getAuthorUrl(this.props.author)}>{this.props.author}</a></span>;
...which obviates the need for keys.
Here's the former solution in a working snippet:
const getAuthorUrl = author => `/${author.toLowerCase()}`;
class Foo extends React.Component {
_renderAuthor() {
if (!this.props.author) {
return null;
}
return [
<span key="by"> by </span>,
<a key="author" href={getAuthorUrl(this.props.author)}>{this.props.author}</a>,
];
}
render() {
return (
<div>
{this.props.datePosted}
{this._renderAuthor()}
</div>
);
}
}
ReactDOM.render(<Foo datePosted="Today" author="Me"/>, 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>

It's not currently possible to do this without some sort of workaround like wrapping everything in another component, since it ends up with the underlying React code trying to return multiple objects.
See this active Github issue where support for this is being considered for a future version though.
Edit: You can now do this with Fragments in React 16, see:
https://reactjs.org/blog/2017/11/28/react-v16.2.0-fragment-support.html

There is another way to solve this. I will suggest you create another component Author.js:
function Author(props) {
return (<span>
<span> by </span>
<a href={props.getAuthorUrl(props.author)}>{props.author}</a>
</span>)
}
class Foo extends React.Component {
render() {
return (
<div>
{this.props.title}
{this.props.author && <Author author={this.props.author} getAuthorUrl={this.getAuthorUrl} />}
</div>
);
}
}
I didn't test this code though. But it will look more cleaner I think. Hope it helps.

I like to have an If-component around for such things, and I have wrapped everything into a span, as it doesn't really break anything and makes the need for keys go away...
const getAuthorUrl = author => `/${author.toLowerCase()}`;
function If({condition,children}) {
return condition ? React.Children.only(children) : null;
}
class Foo extends React.Component {
render() {
return (
<div>
{this.props.datePosted}
<If condition={this.props.author}>
<span> by
<a key="author" href={getAuthorUrl(this.props.author)}>
{this.props.author}
</a>
</span>
</If>
</div>
);
}
}
ReactDOM.render(<Foo datePosted="Today" author="Me"/>, 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>
...skipping the array thing altogether?

This is a bit hacky but it doesn't have unnecessary jsx as you wished.
var author = 'Daniel';
var title = 'Hello';
var Hello = React.createClass({
_renderAutho0r: function() {
if (!author) {
return null;
}
return {author}
},
render: function() {
var by = author ? ' by ' : null;
return (
<div>
{title}
{by}
{this._renderAutho0r()}
</div>
);
}
});
React.render(<Hello name="World" />, document.body);
my JSFiddle

You can return fragments from sub-rendering functions but not from the main render function, at least before React 16. In order to do so, return an array of components. You don't need to set keys manually unless your fragment children will change (arrays are keyed with indices by default).
For creating fragments you may also use createFragment.
For inline usage, you may use an array or leverage immediately invoked arrow function.
See the example below:
const getAuthorUrl = author => `/${author.toLowerCase()}`;
class Foo extends React.Component {
constructor() {
super();
this._renderAuthor = this._renderAuthor.bind(this);
this._renderUser = this._renderUser.bind(this);
}
_renderAuthor() {
if (!this.props.author) {
return null;
}
return [
' by ',
<a href={getAuthorUrl(this.props.author)}>{this.props.author}</a>,
];
}
_renderUser() {
return [
<h2>{this.props.user.name}</h2>,
<p>{this.props.user.info}</p>
]
}
render() {
return (
<div>
{this.props.datePosted}
{this._renderAuthor()}
<div>
{this.props.user
? this._renderUser()
: <p>User not found</p>}
</div>
<div>
{this.props.user
? [
<h2>{this.props.user.name}</h2>,
<p>{this.props.user.info}</p>
]
: <p>User not found</p>}
</div>
<div>
{this.props.user
? (() => [
<h2>{this.props.user.name}</h2>,
<p>{this.props.user.info}</p>
])()
: <p>User not found</p>}
</div>
</div>
);
}
}
ReactDOM.render(<Foo datePosted="Today" author="Me" user={{name: 'test', info: 'info'}} />, document.getElementById('container'));
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react-dom.min.js"></script>
<div id="container"></div>
In order to not get warnings each child must be assigned a key. In order to do so, instead of returning an array please use helper function fragment(...children) to assign index-based keys automatically. Please note that strings must be converted to spans or other nodes that can be assigned with a key:
const fragment = (...children) =>
children.map((child, index) =>
React.cloneElement(
typeof child === 'string'
? <span>{child}</span>
: child
, { key: index }
)
)
const getAuthorUrl = author => `/${author.toLowerCase()}`;
const fragment = (...children) =>
children.map((child, index) =>
React.cloneElement(
typeof child === 'string'
? <span>{child}</span>
: child
, { key: index }
)
)
class Foo extends React.Component {
constructor() {
super();
this._renderAuthor = this._renderAuthor.bind(this);
this._renderUser = this._renderUser.bind(this);
}
_renderAuthor() {
if (!this.props.author) {
return null;
}
return fragment(
' by ',
<a href={getAuthorUrl(this.props.author)}>{this.props.author}</a>
);
}
_renderUser() {
return fragment(
<h2>{this.props.user.name}</h2>,
<p>{this.props.user.info}</p>
)
}
render() {
return (
<div>
{this.props.datePosted}
{this._renderAuthor()}
<div>
{this.props.user
? this._renderUser()
: <p>User not found</p>}
</div>
<div>
{this.props.user
? fragment(
<h2>{this.props.user.name}</h2>,
<p>{this.props.user.info}</p>
)
: <p>User not found</p>}
</div>
<div>
{this.props.user
? (() => fragment(
<h2>{this.props.user.name}</h2>,
<p>{this.props.user.info}</p>
))()
: <p>User not found</p>}
</div>
</div>
);
}
}
ReactDOM.render(<Foo datePosted="Today" author="Me" user={{name: 'test', info: 'info'}} />, 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>

Try this:
class Foo extends React.Component {
_renderAuthor() {
return <a href={getAuthorUrl(this.props.author)}>{this.props.author}</a>
}
render() {
return (
<div>
{this.props.title}
{this.props.author && " by "}
{this.props.author && this._renderAuthor()}
</div>
);
}
}

Perhaps a more simple way would be to rethink how you're architecting your application. However, in a more simple way.
You're triggering the warning because you're trying to render from an array and not react elements but directly html. In order to approach this, you would have to do
{this._renderAuthor().map(
(k,i) => (React.addons.createFragment({k}))
) }
React addons createFragment function basically does that, it reduces your html elements into react fragments that you can render.
React createFragment documentation
Alternatively, in a much better approach, you can create an AuthorLink stateless component like this..
function AuthorLink(props) {
return (
<div className="author-link">
<span> by </span>
<a href={props.authorUrl}> {props.author} </a>
</div>
});
}
and use this in your main component's render
render() {
const { author } = this.props;
return (
<div>
{this.props.datePosted}
<AuthorLink url={getAuthorUrl(author)} author={author} />
</div>
);
}

Try this approach on your array:
return [
<span key={'prefix-'+random_string_generator()}>' by '</span>,
<a key={'prefix-'+random_string_generator()} href={getAuthorUrl(this.props.author)}>{this.props.author}</a>,
];