ReactJs - Conditional Rendering or hiding component

Generally in React it is better to not render something than to render it as hidden. Here is one related discussion: https://discuss.reactjs.org/t/conditional-rendering-or-toggling-hidden-classes/2535/6

You can change initial state value of isHidden or something like that . When you click button value will be oppasite of before situtation . And when you wants to render you should give condition ;

{ isHidden &&

...

My prefer two methodes:

#1 Element Variables

const button = <LogoutButton onClick={this.handleLogoutClick} />;

<div>
    <Greeting isLoggedIn={isLoggedIn} />
    {button}
</div>

2# Inline If with Logical && Operator

{unreadMessages.length > 0 &&
    <h2>
        You have {unreadMessages.length} unread messages.
    </h2>
}

More details here: https://reactjs.org/docs/conditional-rendering.html

I would go for the "updating state" approach. That way you always have the actual filterItems that is showing in the state. So your components state is in sync and represents the current UI that is showing.

Guess there's no right or wrong in this question though =)

It would make more sense to not render the items that should not be shown until after the Show More has been clicked, and the state has updated. This way you can handle how many items should be shown by default before clicking Show More. This way instead of applying inline styles, or a special class to certain elements, you can use the exact same logic to all FilterItems, but only render X of them.

Generally, there is no significant performance differences between display: none and conditional rendering, because the browser's behaviour in both cases is nearly the same. The main difference is that if you use display: none, then node is not removing from the DOM tree, which forces some CSS pseudo-selectors like :last-child to consider a hidden node as last-child and so on. So, it is not performance-related, but mostly CSS-related. Both of approaches are ok for use, I suppose :)

An other approach based on Array.prototype.slice() method

The usage in parent component

import React from "react";
import { ColorList } from "./Color";

export default function App() {
  return <ColorList colors={["red", "green", "blue"]} visibleItemsCount={1} />;
}

And the ColorList component looks like this:

import React from "react";

// This is just a placeholder component :)
function Color({ color }) {
  return <div style={{ color }}>{color}</div>;
}

export function ColorList({ colors, visibleItemsCount = 0 }) {
  const [showMore, setShowMore] = React.useState(false);

  // Toggle value on click button
  const onClick = () => setShowMore((value) => !value);

  // Memoize the color list when props changed
  const visibleColors = React.useMemo(() => {
    // If show more items, return the whole array
    // Otherwise, return a sliced array based on visible items
    const count = showMore ? colors.count : visibleItemsCount;
    return colors.slice(0, count);
  }, [colors, visibleItemsCount, showMore]);

  console.log(visibleColors);
  return (
    <>
      <h1>Color list</h1>
      <>
        {visibleColors.map((color) => (
          <Color key={color} color={color} />
        ))}
      </>
      <button onClick={onClick}>{showMore ? "Show less" : "Show more"}</button>
    </>
  );
}

Note: I uploaded the code on CodeSandbox, you can check it here

You could use a library called react-if. This library helps you wether to render or not based on a a condition.

Here is an example:

const Bar = ({ name, age, drinkingAge }) => (
    <div>
        <Header />
        <If condition={ age >= drinkingAge }>
            <Then><span className="ok">Have a beer, {name}!</span></Then>
            <Else><span className="not-ok">Sorry, {name}, you are not old enough.</span></Else>
        </If>
        <Footer />
    </div> )