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To open a file input box on button click in React:

1. Set the property on the button element onClick.
2. Set the property on the file input ref.
3. When the button is clicked, open the file input box, eg inputRef.current.click().

App.js

import {useRef} from 'react';

const App = () => {
  const inputRef = useRef(null);

  const handleClick = () => {
    // 👇️ open file input box on click of other element
    inputRef.current.click();
  };

  const handleFileChange = event => {
    const fileObj = event.target.files && event.target.files[0];
    if (!fileObj) {
      return;
    }

    console.log('fileObj is', fileObj);

    // 👇️ reset file input
    event.target.value = null;

    // 👇️ is now empty
    console.log(event.target.files);

    // 👇️ can still access file object here
    console.log(fileObj);
    console.log(fileObj.name);
  };

  return (
    <div>
      <input
        style={{display: 'none'}}
        ref={inputRef}
        type="file"
        onChange={handleFileChange}
      />

      <button onClick={handleClick}>Open file upload box</button>
    </div>
  );
};

export default App;

We use the useRef hook to access the file input element.

请注意, we have to access the property refof the object currentto access the file input element on which we set the ref attribute.

When we pass the ref prop to an element, like, React sets the .current property of the ref object to the corresponding DOM node.

We can call click()methods such as ref.current.click()to simulate a mouse click on a file input element.

When the method is used on an element click(), it triggers the element's click event. When the file input's click event is triggered, the file upload dialog opens.

请注意, we set the file input's display property to none to hide it.

Now, when the user clicks on the button element, we simulate a click on the file input using the ref object and the file upload box opens.

This approach works for any type of element, such as an divor an icon. Simply set the attribute on the element onClickand simulate a click on the file input when the element is clicked.