useState hook in React

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import React, { useState } from 'react';
 
function Example() {
  // useState hook. Declare a new state variable, in the top level only. Called every time on render.
  const [count, setCount] = useState(0);
  // The default value is run only once. Not on every render.
  const [count, setCount] = useState(() => 0);
  // Object as a value of state.
  const [objState, setObjState] = useState({ count: 0, name: 'Object State' });
 
  function increaseCount() {
    // Can't run more than once.
    setCount(count + 1);
    // Can run multiple times, this is a better way to set state.
    setCount((prevCount) => prevCount + 1);
    // Setting object values doesn't merge the values automatically, so this code will delete name property of our object.
    setCount((prevObjState) => { count: prevObjState.count + 1 });
    // Correct way to update object.
    setCount((prevObjState) => { ...prevObjState, count: prevObjState.count + 1 });
  }
 
  return (
    <div>
      <p>You clicked {count} times</p>
      <button onClick={increaseCount}>
        Click me
      </button>
    </div>
  );
}
Programming Language: ECMAScript