Why the constructor matters

In a class component, the constructor is that initial setup step. It’s where you call super(props), set initial state, and bind event handlers (if you’re not using arrow functions). Without this, your component might run into unexpected bugs—state might be undefined, this might not refer to the component instance, or your handlers might lose context.

Think of it like the foundation of your component: you lay the groundwork here so the rest of the component behaves predictably.
React components are the basic units of user interfaces. Component architecture relates to how you organize those units in a way that is predictable and maintainable.

If you understand what a constructor solves, you'll be more able to determine if class components, class fields, or hooks are appropriate for the next feature you're working on.

What you typically do in the constructor

Here are the key responsibilities:

• Calling super(props): This ensures that the parent class’s (i.e., React.Component) constructor runs, which makes this.props available.
• Initializing this.state: If your component needs any initial state, you set it up here.
• Binding event handlers: If you use traditional methods and refer to this inside them, you’ll often bind them here so this stays correct when the method is used as a callback.

Properly done, this gives your component a clean starting point.

When you might not need a constructor

If your component is simple, or you’re using functional components with hooks (e.g., useState, useEffect), you might skip a constructor altogether. React’s shift toward functional components means fewer new components rely on constructors. But if you’re maintaining older code, working with existing class-components, or just want to understand the full architecture, constructors still matter.

Understanding the constructor in class components helps you write more reliable React apps. Even if you mostly work with functional components today, knowing how it works is valuable—especially when you encounter legacy code or need to lead a migration.