A Clean Way to Conditionally Render Components

Today, I want to share a clean way to conditionally render child components while using React. It's very simple.

Live Demo:
https://codesandbox.io/s/if-component-demo-9iipl?file=/src/App.js

Before

function App(){
  // ...
  return <div>
      {someCondition?
      <SomeChildA>
        <div>Some Contents</div>
        <div>Some Contents</div>
        <div>Some Contents</div>
      </SomeChildA>
      : 
      <SomeChildB>
        <div>Some Contents</div>
        <div>Some Contents</div>
        <div>Some Contents</div>
      </SomeChildB>}
    </div>
}

After

function App(){
  // ...
  return <div>
      <If condition={someCondition}>
        <SomeChildA>
          <div>Some Contents</div>
          <div>Some Contents</div>
          <div>Some Contents</div>
        </SomeChildA>
      </If>
      <If condition={!someCondition}>
        <SomeChildB>
          <div>Some Contents</div>
          <div>Some Contents</div>
          <If condition={someOtherCondition}>
            <NestExample/>
          </If>
          <div>Some Contents</div>
        </SomeChildB>
      </If>
    </div>
}

<If/> Component

function If(props) {
    return props.condition ? <>{props.children}</> : null;
}

Thanks for reading! Have a nice day!

Comments

[moorerichard]

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[Hendrik Volschenk]

I wanted to add the same comment about the content of the <If> being evaluated immediately
and got some quite surprising results.

See here: codesandbox.io/s/if-component-b5zxk

[Anxiny]

Yes, a good example of how it works

[Martin Pham]

Your idea is nice. However I think having an component would be overkill. Since the embed conditional rendering is already good.

I’d like to add a bit. Since you want to render the ComponentX only with some conditions, it’d be better if you could lazy load it. So it will be downloaded only when we need, therefore downsize the initial bundle. Lazy and Suspense can help you to do it.

[Igor Bykov]

Just out of curiosity: do you really think that evaluation of a control-flow-like one-liner might turn into a bottleneck in a react app?

I mean, I'm agree that this approach might be error prone if one works with deeply nested & all-levels fully optional objects/arrays (which isn't the most common use case in the world by the way) but do you think it may anyhow affect the rendering performance?

I mean, it seems unlikely that someone would just accidentially stitch in all DOOM engine logic re-written & adapted for JS in-between the <If></If>, isn't it?

[Anxiny]

I just don't like the {...} things inside my JSX, it just doesn't look nice in terms of format.

[cyrstron]

IMO, the best way of doing that is this pattern

    condition && (
        <Component />
    )

Much more concise, decently readable and short circuit saves some resources and possible runtime errors with not evaluating jsx.

[Anxiny]

Yes, it will cause an error. But it helps you write code in a more clean way. For example:

Since you will get an error by doing this way.

export default function App() {
  const [person, setData] = useState(null);

  return (
    <div className="App">
      <If condition={person}>
        <h4>{person.name}</h4>
        <p>{person.bio}</p>
        <ul>
          {person.attrs.map(({ name, value }) => {
            return <li key={name}>{value}</li>;
          })}
        </ul>
      </If>
    </div>
  );
}

It forced you to do things like this which results a cleaner code:

export default function App() {
  const [person, setData] = useState(null);

  return (
    <div className="App">
      <If condition={person}>
        <PersonCard person={person} />
        <OtherThingThatUsePerson person={person}/>
      </If>
    </div>
  );
}

function PersonCard({ person }) {
  return (
    <div>
      <h4>{person.name}</h4>
      <p>{person.bio}</p>
      <ul>
        {person.attrs.map(({ name, value }) => {
          return <li key={name}>{value}</li>;
        })}
      </ul>
    </div>
  );
}

Also, you can always check each property, but that is not recommended

<If condition={person.name}>...</If>

[Kwanele]

thanks. this opened my eyes

[Hendrik Volschenk]

I agree with @lukeshiru - This solution is really expensive. If you want to do this I would highly suggest you use a render prop.

[Anxiny]

Thanks for the feedback.
I don't think is good idea to put heavy task in the render return anyway so the performance does not suffer much by having a If wrappers.

If you have a case that may cause performance issue, please let me know

[Anxiny]

Yes, the statement in <If/> will be evaluated, but I feel it is minor problem that can be avoid, for example, enclosing the statement inside the child component.

Thanks for point this out!

[Lukas Elmer]

Beside the performance issue, this can be an issue if you check in the condition a precondition for the rendering (e.g. if an object exists), and in the rendering part you depend on this check (e.g. access properties of this object).

E.g. let post: Post | undefined
Check in the condition if post !== undefined
Render post.title if the condition is true

[Bernd Wechner]

Forgive the total newb question but what is going on here? I have never seen naked HTML used like that in a Javascript function. What's going on there?

[Anxiny]

The function here is used in ReactJS environment.
It's a functional component in React.
This format is called JSX.

Best

[Bernd Wechner]

Thanks for clarifying. I'd make sure to mention that in the article but perhaps the series is in that context and I just surfed in at a single chapter out of context. Not an unusual use case though so I'd aim to include a very brief intro in each chapter to make a newcomer aware of context I guess.

[Anxiny]

Thanks for point that out!
I will edit the post to add that.

Best

[Bernd Wechner]

All good. Nice article. Alas I don't use React hence clueless on that syntax ;-). But a learning all the same. That's why dev.to is so nice.

[Anxiny]

If you mean the render of <If/> component will be executed regardless of the condition, that is true. But I don't think it will cause any error itself.

For performance, so far I don't feel any drawback of using this approach since it does not render its children when condition if false as I mentioned previously.
It should be very similar to the <Route/> in React-Router.

Best

[Anxiny]

Thanks for the feedback!
I'm not sure if I understand you reply correctly, but here is demo that shows the child component will not be rendered unless the condition is true.

codesandbox.io/s/if-component-demo...

export default function App() {
  const [data, setData] = useState(null);

  return (
    <div className="App">
      {data ? <Child name="A" /> : <Child name="NO DATA" />}
      <If condition={data}>
        <Child name="Has Data" />
      </If>
      <If condition={data}>
        <ChildNeedsData data={data} />
      </If>
    </div>
  );
}

function Child(props) {
  useEffect(() => {
    console.log(`Child ${props.name} is rendered`);
    return () => console.log(`Child ${props.name} is unmounted`);
  }, []);
  console.log(`Child ${props.name} is rendering`);
  return <div>Child {props.name}</div>;
}

function ChildNeedsData(props) {
  return <h4>{props.data.name}</h4>;
}

Output

Child NO DATA is rendering 
Child NO DATA is rendered 
// No Error while running is demo

If you change the code to this:

      <If condition={!data}>
        <ChildNeedsData data={data} />
      </If>

You will get a error.