How to Fix TypeError: document.querySelector(...) is null in React Apps

Learn how to handle input values in React without using `querySelector()`, a common pitfall for developers. Discover the best practices and a better solution for fetching user input effectively!
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Understanding the Problem

Imagine you have an input field in your React application that you want to fetch user input from. Here’s a snippet of code you might be using:

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What’s Going Wrong?

When the above code executes, if the # searchQ element isn't yet rendered when this line is run:

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You'll encounter the error because querySelector() returns null when it can't find the specified element. In React, since rendering happens asynchronously, there’s a high chance the input field hasn't mounted yet when the code runs.

The Best Practice: Using React's useEffect Hook

Using selectors like querySelector() is generally considered a bad practice in React unless in very specific circumstances. Instead, you can manage the component’s state more effectively by utilizing the useEffect and useState hooks. Let's see how:

Step 1: Setting Up State

First, we’ll set up a state variable to store the input value, along with a reference for the paragraph element where we want to display the input value:

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Step 2: Handling Input Changes

Set up a function to update the state each time the user types in the input field:

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Step 3: Submitting the Form

Now, let’s create the submission function that will prevent the default form behavior and log/display the input value:

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Step 4: Putting It All Together

Here’s how your component might look when all these parts are put together:

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Explanation of Changes

useState: This hook holds the current value of the input field, allowing React to manage state.

onChange: Every time the input changes, the handleChange function updates the state.

useRef: Reference is created for the paragraph element to directly manipulate its properties without using selectors.

handleSubmit: When the form is submitted, this function prevents the default action and showcases the value in the designated paragraph.

Conclusion

Happy coding!