I want to pass through the

const [imageurl, setImageurl] = useState<string>('');

after setting a value to imageurl between my .tsx files. How can i do it?

I tried exporting the variables at out of main function but it worked without the values.

I want to pass through the

const [imageurl, setImageurl] = useState<string>('');

after setting a value to imageurl between my .tsx files. How can i do it?

I tried exporting the variables at out of main function but it worked without the values.

• javascript
• reactjs
• react-native
• expo

• 2 Please provide enough code so others can better understand or reproduce the problem. – tanaydin Commented Mar 15 at 22:27
• If you're using useState then realistically what you should be doing is passing that down to a React component. If you're trying to import that from an export you're using things in very unintended and inadvisable ways. – Slbox Commented Mar 15 at 23:22

1 Answer 1

Understanding Variables vs. State in React

The Difference Between Variables and State

In React, there's a fundamental difference between regular variables and state:

Regular Variables:

• Are re-initialized every render
• Changes don't trigger re-renders
• Values are lost between renders

React State:

• Persists between renders
• Changes trigger component re-renders
• Managed by React's state management system

What is State in React?

State is a built-in React object that allows components to create and manage their own data. Unlike props (which are passed down from parent components), state is internal to a component and can be changed by the component itself.

When you call useState(), you're telling React to:

1. Remember a value between renders
2. Provide a way to update that value
3. Re-render the component when that value changes

// This creates a state variable "imageurl" with an initial value of ''
// and a function "setImageurl" that can update it
const [imageurl, setImageurl] = useState<string>('');

Sharing State Between Components

To pass state between components, you have a few options:

Option 1: Props (for parent-to-child sharing)

// ParentComponent.tsx
function ParentComponent() {
  const [imageurl, setImageurl] = useState<string>('');
  
  // Set the image URL
  const handleImageSelect = () => {
    setImageurl('https://example/image.jpg');
  };
  
  return (
    <>
      <button onClick={handleImageSelect}>Select Image</button>
      <ChildComponent imageurl={imageurl} />
    </>
  );
}

// ChildComponent.tsx
function ChildComponent({ imageurl }) {
  return <img src={imageurl} />;
}

Option 2: Lifting State Up (for sibling components)

// ParentComponent.tsx
function ParentComponent() {
  const [imageurl, setImageurl] = useState<string>('');
  
  return (
    <>
      <ImageSelector setImageurl={setImageurl} />
      <ImageDisplay imageurl={imageurl} />
    </>
  );
}

// ImageSelector.tsx
function ImageSelector({ setImageurl }) {
  const handleSelect = () => {
    setImageurl('https://example/image.jpg');
  };
  
  return <button onClick={handleSelect}>Select Image</button>;
}

// ImageDisplay.tsx
function ImageDisplay({ imageurl }) {
  return <img src={imageurl} />;
}

Option 3: Context API (for distant components)

// ImageContext.tsx
import { createContext, useState, ReactNode } from 'react';

type ImageContextType = {
  imageurl: string;
  setImageurl: (url: string) => void;
};

export const ImageContext = createContext<ImageContextType>({
  imageurl: '',
  setImageurl: () => {},
});

export function ImageProvider({ children }: { children: ReactNode }) {
  const [imageurl, setImageurl] = useState<string>('');
  
  return (
    <ImageContext.Provider value={{ imageurl, setImageurl }}>
      {children}
    </ImageContext.Provider>
  );
}

// App.tsx
import { ImageProvider } from './ImageContext';

function App() {
  return (
    <ImageProvider>
      <SomeComponent />
      <OtherComponent />
    </ImageProvider>
  );
}

// SomeComponent.tsx
import { useContext } from 'react';
import { ImageContext } from './ImageContext';

function SomeComponent() {
  const { setImageurl } = useContext(ImageContext);
  
  const handleSelect = () => {
    setImageurl('https://example/image.jpg');
  };
  
  return <button onClick={handleSelect}>Select Image</button>;
}

// OtherComponent.tsx
import { useContext } from 'react';
import { ImageContext } from './ImageContext';

function OtherComponent() {
  const { imageurl } = useContext(ImageContext);
  
  return <img src={imageurl} />;
}

Option 4: State Management Libraries

For more complex applications, consider using state management libraries like Redux, Zustand, or Jotai.

Common Mistakes

Mistake: Exporting the state variable directly

// THIS WON'T WORK as expected
export const [imageurl, setImageurl] = useState<string>('');

This doesn't work because:

1. Hooks can only be called inside React function components
2. Each component that imports this would share the same state
3. React's state management expects hooks to be called during component rendering

Summary

1. Use state for values that change and need to trigger re-renders
2. Pass state down to child components using props
3. For sharing state between sibling components, lift state up to their common parent
4. For distant components, use Context API or a state management library

Choose the approach that best fits your application's complexity and component structure.