JSX is a powerful extension to JavaScript that allows us to define UI components. But it doesn’t support loops or conditional expressions directly (although the addition of conditional expressions has been discussed before).
If you want to iterate over a list to render more than one component or implement some conditional logic, you have to use pure JavaScript. You don’t have a lot of options with looping, either. Most of the time, map will cover your needs.
But conditional rendering? That’s another story.
What is conditional rendering in React?
In React, conditional rendering refers to the process of delivering elements and components based on certain conditions.
There’s more than one way to use conditional rendering in React. As with most things in programming, some are better suited than others depending on the problem you’re trying to solve.
This tutorial covers the most popular ways to implement conditional rendering in React:
How to write if...else in React
Prevent rendering with null
React element variables
The ternary operator in React
Short-circuit AND operator (&&)
Immediately invoked function expressions (IIFEs)
React subcomponents
Enum objects
Higher-order components (HOCs) in React
We’ll also review some tips and best practices for implementing conditional rendering in React, including:
Performance considerations
Conditional rendering with fragments
Conditional rendering with React Hooks
Deciding how to implement conditional rendering in React
To demonstrate how all these methods work, we’ll implement a component with a view/edit functionality:
You can try and fork all the examples in JSFiddle.
We’ll start with the most naive implementation using an if...else block and build it from there.
1. How to write if...else in React
Create a component with the following state:
class App extends React.Component {
constructor(props) {
super(props);
this.state = {text: '', inputText: '', mode:'view'};
}
}
You’ll use one property for the saved text and another for the text that is being edited. A third property will indicate if you are in edit or view mode.
Next, add some methods for handling input text and then save and edit events:
class App extends React.Component {
constructor(props) {
super(props);
this.state = {text: '', inputText: '', mode:'view'};
this.handleChange = this.handleChange.bind(this);
this.handleSave = this.handleSave.bind(this);
this.handleEdit = this.handleEdit.bind(this);
}
handleChange(e) {
this.setState({ inputText: e.target.value });
}
handleSave() {
this.setState({text: this.state.inputText, mode: 'view'});
}
handleEdit() {
this.setState({mode: 'edit'});
}
}
Now, for the render method, check the mode state property to either render an edit button or a text input and a save button, in addition to the saved text:
class App extends React.Component {
// …
render () {
if(this.state.mode === 'view') {
return (
<div>
<p>Text: {this.state.text}</p>
<button onClick={this.handleEdit}>
Edit
</button>
</div>
);
} else {
return (
<div>
<p>Text: {this.state.text}</p>
<input
onChange={this.handleChange}
value={this.state.inputText}
/>
<button onClick={this.handleSave}>
Save
</button>
</div>
);
}
}
Here’s the complete Fiddle to try it out:
An if...else block is the easiest way to solve the problem, but I’m sure you know this is not a good implementation.
It works great for simple use cases, and every programmer knows how it works. But there’s a lot of repetition, and the render method looks crowded.
So let’s simplify it by extracting all the conditional logic to two render methods: one to render the input box and another to render the button.
class App extends React.Component {
// …
renderInputField() {
if(this.state.mode === 'view') {
return <div></div>;
} else {
return (
<p>
<input
onChange={this.handleChange}
value={this.state.inputText}
/>
</p>
);
}
}
renderButton() {
if(this.state.mode === 'view') {
return (
<button onClick={this.handleEdit}>
Edit
</button>
);
} else {
return (
<button onClick={this.handleSave}>
Save
</button>
);
}
}
render () {
return (
<div>
<p>Text: {this.state.text}</p>
{this.renderInputField()}
{this.renderButton()}
</div>
);
}
}
Here’s the complete Fiddle to try it out:
If we have more than two branches that depend on the same variable to evaluate the condition, instead of having a big if...else block:
if(this.state.mode === 'a') {
// ...
} else if(this.state.mode === 'b') {
// ...
} else if(this.state.mode === 'c') {
// ...
} else {
// ...
}
We can use a switch statement:
switch(this.state.mode) {
case 'a':
// ...
case 'b':
// ...
case 'c':
// ...
default:
// equivalent to the last else clause ...
}
It may add a bit more clarity, but:
It’s still too verbose
It doesn’t work with multiple/different conditions
Just like an if...else statement, you can’t use it inside of return statement with JSX (except when you use immediately invoked functions, which I’ll cover later)
Let’s look at some additional techniques to improve this code.
Notice that the method renderInputField returns an empty <div> element when the app is in view mode. This is not necessary, however.
2. Prevent rendering with null
If you want to hide a component, you can make its render method return null, so there’s no need to render an empty (and different) element as a placeholder. One important thing to keep in mind when returning null, however, is that even though the component doesn’t show up, its lifecycle methods are still fired.
Take, for example, the following Fiddle, which implements a counter with two components:
The Number component only renders the counter for even values; otherwise, null is returned. When you look at the console, however, you’ll see that componentDidUpdate is always called regardless of the value returned by render.
componentDidUpdate
Back to our example, change the renderInputField method to look like this:
renderInputField() {
if(this.state.mode === 'view') {
return null;
} else {
return (
<p>
<input
onChange={this.handleChange}
value={this.state.inputText}
/>
</p>
);
}
}
Here’s the complete Fiddle:
One advantage of returning null instead of an empty element is that you’ll improve the performance of your app a little bit because React won’t have to unmount the component to replace it.
For example, when trying the Fiddle that renders the empty <div> element, if you open the Inspector tab, you’ll see how the <div> element under the root is always updated:
Unlike the case when null is returned to hide the component, where that <div> element is not updated when the Edit button is clicked:
Learn more about reconciliation in React, which basically refers to how React updates the DOM elements and how the diffing algorithm works.
Maybe in this simple example, the performance improvement is insignificant, but when working when big components, there can be a difference. I’ll talk more about the performance implications of conditional rendering later. For now, let’s continue to improve this example.
3. React element variables
One thing I don’t like is having more than one return statement in methods, so I’m going to use a variable to store the JSX elements and only initialize it when the condition is true:
renderInputField() {
let input;
if(this.state.mode !== 'view') {
input =
<p>
<input
onChange={this.handleChange}
value={this.state.inputText} />
</p>;
}
return input;
}
renderButton() {
let button;
if(this.state.mode === 'view') {
button =
<button onClick={this.handleEdit}>
Edit
</button>;
} else {
button =
<button onClick={this.handleSave}>
Save
</button>;
}
return button;
}
This gives the same result as returning null from those methods. Here’s the Fiddle to try it out:
The main render method is more readable this way, but maybe it isn’t necessary to use if...else blocks (or something like a switch statement) and secondary render methods. Let’s try a simpler approach.
4. The ternary operator in React
Instead of using an if...else block, we can use the ternary conditional operator:
condition ? expr_if_true : expr_if_false
The operator is wrapped in curly braces, and the expressions can contain JSX, optionally wrapped in parentheses to improve readability. It can also be applied in different parts of the component.
Let’s apply it to the example so you can see this in action. I’m going to remove renderInputField and renderButton, and in the render method, I’m going to add a variable to know if the component is in view or edit mode:
render () {
const view = this.state.mode === 'view';
return (
<div>
</div>
);
}
Now you can use the ternary operator to return null if the view mode is set, or the input field otherwise:
// ...
return (
<div>
<p>Text: {this.state.text}</p>
{
view
? null
: (
<p>
<input
onChange={this.handleChange}
value={this.state.inputText} />
</p>
)
}
</div>
);
Using a ternary operator, you can declare one component to render either a save or edit button by changing its handler and label correspondingly:
// ...
return (
<div>
<p>Text: {this.state.text}</p>
{
...
}
<button
onClick={
view
? this.handleEdit
: this.handleSave
} >
{view ? 'Edit' : 'Save'}
</button>
</div>
);
Here’s the Fiddle to try it out:
As mentioned before, this operator can be applied in different parts of the component, even inside return statements and JSX, acting as a one-line if...else statement. However, exactly for this reason, things can get messy quickly.
Let’s review another technique that can help improve the code.
5. Short-circuit AND operator (&&)
The ternary operator has a special case where it can be simplified. When you want to render either something or nothing, you can only use the && operator. Unlike the & operator, && doesn’t evaluate the right-hand expression if evaluating only the left-hand expression can decide the final result.
For example, if the first expression evaluates to false (false && …), it’s not necessary to evaluate the next expression because the result will always be false.
In React, you can have expressions like the following:
return (
<div>
{ showHeader && <Header /> }
</div>
);
If showHeader evaluates to true, the <Header/> component will be returned by the expression. If showHeader evaluates to false, the <Header/> component will be ignored, and an empty <div> will be returned.
This way, the following expression:
{
view
? null
: (
<p>
<input
onChange={this.handleChange}
value={this.state.inputText} />
</p>
)
}
Can be turned into:
!view && (
<p>
<input
onChange={this.handleChange}
value={this.state.inputText} />
</p>
)
Here’s the complete Fiddle:
Looks better, right?
However, the ternary operator doesn’t always look better. Consider a complex, nested set of conditions:
return (
<div>
{ condition1
? <Component1 />
: ( condition2
? <Component2 />
: ( condition3
? <Component3 />
: <Component 4 />
)
)
}
</div>
);
This can become a mess pretty quickly. For that reason, sometimes you might want to use other techniques, like immediately invoked functions.
6. Immediately invoked function expressions (IIFEs)
As the name implies, immediately invoked function expressions (IIFEs) are functions that are executed immediately after they are defined — there’s no need to call them explicitly.
Generally, this is how you define and execute (at a later point) a function:
function myFunction() {
// ...
}
myFunction();
But if you want to execute the function immediately after it is defined, you have to wrap the whole declaration in parentheses (to convert it to an expression) and execute it by adding two more parentheses (passing any arguments the function may take).
Either this way:
( function myFunction(/* arguments */) {
// ...
}(/* arguments */) );
Or this way:
( function myFunction(/* arguments */) {
// ...
} ) (/* arguments */);
Since the function won’t be called in any other place, you can drop the name:
( function (/* arguments */) {
// ...
} ) (/* arguments */);
Or you can also use arrow functions:
( (/* arguments */) => {
// ...
} ) (/* arguments */);
In React, you use curly braces to wrap an IIFE, put all the logic you want inside it (if...else, switch, ternary operators, etc.), and return whatever you want to render.
In other words, inside an IIFE, we can use any type of conditional logic. This allows us to use if...else and switch statements inside return statements and JSX if you consider it to improve the readability of the code.
return (
<div>
<p>...</p>
{
(()=> {
switch (condition) {
case 1: return <Component1 />;
case 2: return <Component2 />;
default: null;
}
})()
}
</div>
);
For example, here’s how the logic to render the save/edit button could look with an IIFE:
{
(() => {
const handler = view
? this.handleEdit
: this.handleSave;
const label = view ? 'Edit' : 'Save';
return (
<button onClick={handler}>
{label}
</button>
);
})()
}
7. React subcomponents
Sometimes, an IFFE might seem like a hacky solution. After all, we’re using React — the recommended approaches are to split up the logic of your app into as many components as possible and to use functional programming instead of imperative programming.
So moving the conditional rendering logic to a subcomponent that renders different things based on its props would be a good option. But here, I’m going to do something a bit different to show you how you can go from an imperative solution to more declarative and functional solutions.
I’m going to start by creating a SaveComponent:
const SaveComponent = (props) => {
return (
<div>
<p>
<input
onChange={props.handleChange}
value={props.text}
/>
</p>
<button onClick={props.handleSave}>
Save
</button>
</div>
);
};
As properties, it receives everything it needs to work. In the same way, there’s an EditComponent:
const EditComponent = (props) => {
return (
<button onClick={props.handleEdit}>
Edit
</button>
);
};
Now the render method can look like this:
render () {
const view = this.state.mode === 'view';
return (
<div>
<p>Text: {this.state.text}</p>
{
view
? <EditComponent handleEdit={this.handleEdit} />
: (
<SaveComponent
handleChange={this.handleChange}
handleSave={this.handleSave}
text={this.state.inputText}
/>
)
}
</div>
);
}
Here’s the complete Fiddle:
If components
There are libraries like jsx-control-statements that extend JSX to add conditional statements like:
<If condition={ a === 1 }>
<span>Hi!</span>
</If>
This library is actually a Babel plugin, so the above code is translated to:
{
a === 1 ? <span>Hi!</span> : null;
}
Or the Choose tag, which is used for more complex conditional statements:
<Choose>
<When condition={ a === 1 }>
<span>One</span>
</When>
<When condition={ a === 2 }>
<span>Two</span>
</When>
<Otherwise>
<span>Default</span>
</Otherwise>
</Choose>
The above translates to:
{
a === 1 ? (
<span>One</span>
) : a === 2 ? (
<span>Two</span>
) : (
<span>Default</span>
);
}
These libraries provide more advanced components, but if we need something like a simple if...else, we can use a solution similar to Michael J. Ryan’s in the comments for this issue:
const If = (props) => {
const condition = props.condition || false;
const positive = props.then || null;
const negative = props.else || null;
return condition ? positive : negative;
};
// …
render () {
const view = this.state.mode === 'view';
const editComponent = <EditComponent handleEdit={this.handleEdit} />;
const saveComponent = <SaveComponent
handleChange={this.handleChange}
handleSave={this.handleSave}
text={this.state.inputText}
/>;
return (
<div>
<p>Text: {this.state.text}</p>
<If
condition={ view }
then={ editComponent }
else={ saveComponent }
/>
</div>
);
}
8. Enums objects
Now that the save/edit functionality is encapsulated in two components, we can also use enum objects to render one of them, depending on the state of the application.
An enum is a type that groups constant values. For example, here’s how you define one in TypeScript:
enum State {
Save = "Some value",
Edit = "Another value"
}
JavaScript doesn’t support enums natively, but we can use an object to group all the properties of the enum and freeze that object to avoid accidental changes.
const State = Object.freeze({
Save: "Some value",
Edit: "Another value"
});
Why not just use constants? Well, the main benefit is that we can use a dynamically generated key to access the property of the object.
const key = condition ? "Save" : "Edit":
const state = State[key];
Applying this to our example, we can declare an enum object with the two components for saving and editing:
const Components = Object.freeze({
view: <EditComponent handleEdit={this.handleEdit} />,
edit: <SaveComponent
handleChange={this.handleChange}
handleSave={this.handleSave}
text={this.state.inputText}
/>
});
And use the mode state variable to indicate which component to show.
const key = this.state.mode;
return (
<div>
<p>Text: {this.state.text}</p>
{
Components[key]
}
</div>
);
You can see the complete code in the following fiddle:
https://jsfiddle.net/eh3rrera/7ey56xud/embedded
Enum objects are a great option when you want to use or return a value based on multiple conditions, making them a great replacement for if...else and switch statements in many cases.
9. Higher-order components (HOCs) in React
A higher-order component (HOC) is a function that takes an existing component and returns a new one with some added functionality:
const EnhancedComponent = higherOrderComponent(component);
Applied to conditional rendering, a HOC could return a different component than the one passed based on some condition:
function higherOrderComponent(Component) {
return function EnhancedComponent(props) {
if (condition) {
return <AnotherComponent { ...props } />;
}
return <Component { ...props } />;
};
}
There’s an excellent article about HOCs by Robin Wieruch that digs deeper into conditional renderings with higher-order components. For this article, I’m going to borrow the concepts of the EitherComponent.
In functional programming, the Either type is commonly used as a wrapper to return two different values. So let’s start by defining a function that takes two arguments, another function that will return a Boolean value (the result of the conditional evaluation), and the component that will be returned if that value is true:
function withEither(conditionalRenderingFn, EitherComponent) {
}
It’s a convention to start the name of the HOC with the word with. This function will return another function that will take the original component to return a new one:
function withEither(conditionalRenderingFn, EitherComponent) {
return function buildNewComponent(Component) {
}
}
The component (function) returned by this inner function will be the one you’ll use in your app, so it will take an object with all the properties that it will need to work:
function withEither(conditionalRenderingFn, EitherComponent) {
return function buildNewComponent(Component) {
return function FinalComponent(props) {
}
}
}
The inner functions have access to the outer functions’ parameters, so now, based on the value returned by the function conditionalRenderingFn, you either return the EitherComponent or the original Component:
function withEither(conditionalRenderingFn, EitherComponent) {
return function buildNewComponent(Component) {
return function FinalComponent(props) {
return conditionalRenderingFn(props)
? <EitherComponent { ...props } />
: <Component { ...props } />;
}
}
}
Or, using arrow functions:
const withEither = (conditionalRenderingFn, EitherComponent) => (Component) => (props) =>
conditionalRenderingFn(props)
? <EitherComponent { ...props } />
: <Component { ...props } />;
This way, using the previously defined SaveComponent and EditComponent, you can create a withEditConditionalRendering HOC and, with this, create an EditSaveWithConditionalRendering component:
const isViewConditionFn = (props) => props.mode === 'view';
const withEditContionalRendering = withEither(isViewConditionFn, EditComponent);
const EditSaveWithConditionalRendering = withEditContionalRendering(SaveComponent);
You can now use it in the render method, passing all the properties needed:
render () {
return (
<div>
<p>Text: {this.state.text}</p>
<EditSaveWithConditionalRendering
mode={this.state.mode}
handleEdit={this.handleEdit}
handleChange={this.handleChange}
handleSave={this.handleSave}
text={this.state.inputText}
/>
</div>
);
}
Conditional rendering in React: Performance considerations
Conditional rendering can be tricky. As I showed you before, the performance of each option can be different. However, most of the time, the differences don’t matter a lot.
But when they do, you’ll need a good understanding of how React works with the virtual DOM and a few tricks to optimizing performance. Here’s a good article about optimizing conditional rendering in React — I totally recommend you read it.
The essential idea is that changing the position of the components due to conditional rendering can cause a reflow that will unmount/mount the components of the app. Based on the example of the article, I created two JSFiddles.
The first one uses an if...else block to show/hide the SubHeader component
The second one uses the short circuit operator (&&) to do the same
Open the Inspector and click on the button a few times. You’ll see how the Content component is treated differently by each implementation.
Here’s how the if...else block treats the component:
Animation Showing How the if/else Block Treats the Content Component
And here’s how the short-circuit operator do it:
Animation Showing How the Short-Circuit Operator Treats the Content Component
Conditional rendering with fragments
How do you render multiple child components depending on a certain condition? The answer is by using fragments.
Fragments allow you to return multiple elements by grouping them without adding an extra node to the document object model (DOM).
You can use fragments with their traditional syntax:
return (
<React.Fragment>
<Button />
<Button />
<Button />
</React.Fragment>
);
Or with their short syntax:
return (
<>
<Button />
<Button />
<Button />
</>
);
That said, when it comes to rendering multiple elements with fragments depending on a condition, you can use any of the techniques described in this article.
For example, you could use the ternary operator this way:
{
view
? null
: (
<React.Fragment>
<Button />
<Button />
<Button />
</React.Fragment>
)
}
Better yet, you could use a short-circuit &&:
{
condition &&
<React.Fragment>
<Button />
<Button />
<Button />
</React.Fragment>
}
You could also encapsulate the rendering of the child elements in a method and use an if or switch statement to decide what to return:
render() {
return <div>{ this.renderChildren() }</div>;
}
renderChildren() {
if (this.state.children.length === 0) {
return <p>Nothing to show</p>;
} else {
return (
<React.Fragment>
{this.state.children.map(child => (
<p>{child}</p>
))}
</React.Fragment>
);
}
}
Conditional rendering with React Hooks
Today, most experienced React developers use Hooks to write components. So instead of having a class like this:
import React, { Component } from 'react';
class Doubler extends Component {
constructor(props) {
super(props);
this.state = {
num: 1,
};
}
render() {
return (
<div>
<p>{this.state.num}</p>
<button onClick={() =>
this.setState({ num: this.state.num * 2 })
}>
Double
</button>
</div>
);
}
}
You can use the useState hook to write the component with a function:
import React from 'react';
function Doubler() {
const [num, setNum] = React.useState(1);
return (
<div>
<p>{num}</p>
<button onClick={() => setNum(num * 2)}>
Double
</button>
</div>
);
}
Just like fragments, you can use any of the techniques described in this article to conditionally render a component that uses Hooks.
function Doubler() {
const [num, setNum] = React.useState(1);
const showButton = num <= 8;
const button = <button onClick={() => setNum(num * 2)}>Double</button>;
return (
<div>
<p>{num}</p>
{showButton && button}
</div>
);
}
The only caveat is that you can’t conditionally call a Hook so it’s not always executed. According to the Hooks documentation:
Don’t call Hooks inside loops, conditions, or nested functions. Instead, always use Hooks at the top level of your React function. By following this rule, you ensure that Hooks are called in the same order each time a component renders. That’s what allows React to correctly preserve the state of Hooks between multiple useState and useEffect calls.
This usually happens with the useEffect hook. You can’t put a condition that could prevent the hook from being called every time the component is rendered, like this:
if (shouldExecute) {
useEffect(() => {
// ...
}
}
You have to put the condition inside the Hook:
useEffect(() => {
if (shouldExecute) {
// ...
}
}, [shouldExecute])
What’s the best way to implement conditional rendering in React?
As with many things in programming, there are many ways to implement conditional rendering in React. I’d say that, with exception of the first method (if...else with many returns), you’re free to choose whatever method you want.
You can decide which one is best for your situation based on:
Your programming style
How complex the conditional logic is
How comfortable you are with JavaScript, JSX, and advanced React concepts (like HOCs)
And, all things being equal, always favor simplicity and readability.
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