Set the value of an Input on Button click in React

Set the value of an Input on Button click in React #

To get the value of an input on button click in React:

Declare a state variable that tracks the value of the input field.
Add an onClick prop to a button element.
When the button is clicked, update the state variable.

App.js

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import {useState} from 'react';

const App = () => {
  const [message, setMessage] = useState('');

  const handleChange = event => {
    setMessage(event.target.value);
  };

  const handleClick = event => {
    event.preventDefault();

    // 👇️ value of input field
    console.log('old value: ', message);

    // 👇️ set value of input field
    setMessage('New value');
  };

  return (
    <div>
      <input
        type="text"
        id="message"
        name="message"
        onChange={handleChange}
        value={message}
      />

      <h2>Message: {message}</h2>

      <button onClick={handleClick}>Click</button>
    </div>
  );
};

export default App;

We used the useState hook to track the value of the input field.

We set the onChange prop on the field, so every time its value changes, the handleChange function is invoked.

In the handleChange function, we update the state of the input field when the user types.

We set the onClick prop on the button element. Every time the button is clicked, the handleClick function is invoked.

To update the state of the input field, we simply update the state variable.

If you need to clear the value of the input field, set it to an empty string.

Alternatively, you can use an uncontrolled input field.

App.js

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import {useRef} from 'react';

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

  function handleClick() {
    // 👇️ update input value
    inputRef.current.value = 'New value';

    // 👇️ access input value
    console.log(inputRef.current.value);
  }

  return (
    <div>
      <input
        ref={inputRef}
        type="text"
        id="message"
        name="message"
      />

      <button onClick={handleClick}>Log message</button>
    </div>
  );
};

export default App;

The example above uses an uncontrolled input. Notice that the input field does not have an onChange prop or value set.

You can pass an initial value to an uncontrolled input with the defaultValue prop. However, this is not necessary and you can omit the prop if you don't want to set an initial value.

When using uncontrolled input fields, we access the input using a ref.

The useRef() hook can be passed an initial value as an argument. The hook returns a mutable ref object whose .current property is initialized to the passed argument.

Notice that we have to access the current property on the ref object to get access to the input element on which we set the ref prop.

When we pass a ref prop to an element, e.g. <input ref={myRef} />, React sets the .current property of the ref object to the corresponding DOM node.

The useRef hook creates a plain JavaScript object, but gives you the same ref object on every render. In other words, it's pretty much a memoized object value with a .current property.

It should be noted that when you change the value of the current property of the ref, no re-renders are caused.

Every time the user clicks on the button in the example, the value of the uncontrolled input gets updated.

You shouldn't set the value prop on an uncontrolled input (an input field that doesn't have an onChange handler) because that would make the input field immutable and you wouldn't be able to type in it.

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Set the value of an Input on Button click in React

Set the value of an Input on Button click in React #

Borislav Hadzhiev