I’ve spent over years building React applications, and if there is one thing I’ve learned, it’s that performance matters.
When your application starts to grow, you might notice that some parts of your UI feel a bit sluggish or laggy.
In most cases, this happens because React is re-rendering components even when the data hasn’t actually changed.
I remember working on a real estate dashboard for a client, where we had thousands of property listings updating in real-time.
The app was crawling until I implemented PureComponent to prevent those unnecessary re-renders.
In this tutorial, I will walk you through the differences between React.Component and React.PureComponent so you can decide which one fits your project.
Understand React.Component
The standard React.Component is the bread and butter of class-based components in the React ecosystem.
When you use a regular component, React does not compare the old props and state with the new ones automatically.
This means every time the parent component re-renders, the child component will also re-render by default.
Example: A Simple New York Stock Ticker
Let’s look at a scenario where we are tracking stock prices for companies like Apple and Microsoft.
Even if the price stays the same for a few seconds, a regular component might still try to update the UI.
import React, { Component } from 'react';
// This is a regular Component
class StockDisplay extends Component {
render() {
console.log("StockDisplay: I am rendering...");
return (
<div style={{ border: '1px solid #ccc', padding: '10px', margin: '10px' }}>
<h3>Wall Street Update</h3>
<p>Symbol: {this.props.symbol}</p>
<p>Price: ${this.props.price}</p>
</div>
);
}
}
class Dashboard extends Component {
constructor(props) {
super(props);
this.state = {
price: 150,
symbol: "AAPL"
};
}
componentDidMount() {
// Simulating an API call that returns the same data
setInterval(() => {
this.setState({
price: 150
});
}, 2000);
}
render() {
return (
<div>
<h1>Investment Portfolio</h1>
<StockDisplay symbol={this.state.symbol} price={this.state.price} />
</div>
);
}
}
export default Dashboard;You can see the output in the screenshot below.
In this example, even though the price stays at $150, the StockDisplay component logs a message to the console every two seconds.
What is React.PureComponent?
React.PureComponent is exactly like a regular component, but it handles the shouldComponentUpdate method for you.
It performs a “shallow comparison” of the current props and state against the new props and state.
If the values are the same, React skips the re-render process for that specific component and its entire child tree.
Example: Optimize the Stock Ticker
I’ve found that switching to PureComponent is the quickest way to gain back performance in data-heavy apps.
Let’s modify our previous Wall Street example to see the difference.
import React, { PureComponent } from 'react';
// Switching to PureComponent
class OptimizedStockDisplay extends PureComponent {
render() {
console.log("OptimizedStockDisplay: I am rendering...");
return (
<div style={{ border: '1px solid #4CAF50', padding: '10px', margin: '10px' }}>
<h3>NASDAQ Live Feed</h3>
<p>Symbol: {this.props.symbol}</p>
<p>Price: ${this.props.price}</p>
</div>
);
}
}
class MarketWatch extends React.Component {
constructor(props) {
super(props);
this.state = {
price: 280,
symbol: "MSFT"
};
}
componentDidMount() {
// This interval updates the state with the SAME value
setInterval(() => {
this.setState({
price: 280
});
}, 2000);
}
render() {
return (
<div>
<h1>Tech Stock Tracker</h1>
<OptimizedStockDisplay symbol={this.state.symbol} price={this.state.price} />
</div>
);
}
}
export default MarketWatch;Now, you will notice that the console log only appears once. React sees that the price is still 280 and decides to skip the render.
Method 1: Implement Manual Optimization
Sometimes, you don’t want to use PureComponent because you need more control over when the update happens.
In my experience, using the shouldComponentUpdate lifecycle method is the best way to handle complex logic.
Let’s say you are building a weather app for Chicago, and you only want to update the UI if the temperature changes by more than 2 degrees.
import React, { Component } from 'react';
class ChicagoWeather extends Component {
shouldComponentUpdate(nextProps) {
// Only update if temperature change is significant
return Math.abs(this.props.temp - nextProps.temp) >= 2;
}
render() {
console.log("Weather View: Checking the skies over Chicago...");
return (
<div>
<h2>Chicago Weather</h2>
<p>Current Temp: {this.props.temp}°F</p>
</div>
);
}
}
export default ChicagoWeather;You can see the output in the screenshot below.
This manual method gives you the flexibility that PureComponent lacks, as PureComponent always checks for any change.
Method 2: Handle Nested Data Objects
One thing I often warn junior developers about is the “Shallow Comparison” trap.
If your props contain a nested object (like a user profile with an address), PureComponent might not work as expected.
This is because it only checks the reference of the object, not the actual values inside it.
Example: The California Voter Registration List
Imagine a list of voters in Los Angeles where each voter is an object.
import React, { PureComponent } from 'react';
class VoterCard extends PureComponent {
render() {
console.log("VoterCard Rendered");
return <div>{this.props.voter.name} from {this.props.voter.city}</div>;
}
}
class VoterList extends React.Component {
constructor() {
super();
this.state = {
voter: { name: "John Doe", city: "Los Angeles" }
};
}
updateCity = () => {
// WRONG WAY: This mutates the state, PureComponent won't see it
const updatedVoter = this.state.voter;
updatedVoter.city = "San Francisco";
this.setState({ voter: updatedVoter });
};
render() {
return (
<div>
<VoterCard voter={this.state.voter} />
<button onClick={this.updateCity}>Move to SF</button>
</div>
);
}
}You can see the output in the screenshot below.
In the example above, the button won’t trigger a re-render in VoterCard because the object reference stayed the same.
To fix this, I always suggest using the spread operator to create a new object reference.
Key Differences Summary
Based on my years of debugging React apps, here is a quick breakdown of how these two behave:
- Rendering: Component re-renders every time; PureComponent only re-renders when props or state change.
- Performance: PureComponent is generally faster but adds a small overhead for the comparison check.
- Logic: Component is better for complex data; PureComponent is perfect for simple, flat data structures.
When to Choose Which?
I usually start with a regular Component or a Functional Component with React.memo.
I only switch to PureComponent when I identify a performance bottleneck using the React DevTools Profiler.
If your component has many children or performs heavy calculations during render, PureComponent is a lifesaver.
However, if your props are constantly changing anyway, the shallow comparison is just a waste of CPU cycles.
I hope you found this comparison useful and that it helps you build faster React applications.
If you have any questions about how to handle specific data structures, feel free to reach out.
I’ve found that once you master these small optimization details, your development process becomes much smoother.
You may also like to read:
- React File Input Component
- How to Convert React Class Components to Functional Components
- How to Modularize React Components
- How to Disable React Strict Mode for One Component
I am Bijay Kumar, a Microsoft MVP in SharePoint. Apart from SharePoint, I started working on Python, Machine learning, and artificial intelligence for the last 5 years. During this time I got expertise in various Python libraries also like Tkinter, Pandas, NumPy, Turtle, Django, Matplotlib, Tensorflow, Scipy, Scikit-Learn, etc… for various clients in the United States, Canada, the United Kingdom, Australia, New Zealand, etc. Check out my profile.
