setState Callback in a Functional Component

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Tue Jun 29 2021 10:03:32 GMT+0000 (UTC)

Saved by @hisam #react.js #javascript #react #usestate

import React, { useEffect, useState } from 'react';

function App() {
  const [age, setAge] = useState(0);
  
  updateAge(value) {
    setDisplayUsaStudents(
            (prevDisplayUsaStudents) => !prevDisplayUsaStudents
          );
    setAge({prevAge: value});
  };

  useEffect(() => {
    if (age !== 0 && age >= 21) {
      // Make API call to /beer
    } else {
      // Throw error 404, beer not found
    }
//the square parentheses with the age state variable inside is called the dependency array. //it tells the useEffect function to listen for any changes to the state of age.
//when age changes, useEffect executes
  }, [age]);

  return (
    <div>
      <p>Drinking Age Checker</p>
      <input
        type="number"
        value={age} 
        onChange={e => setAge(e.target.value)}
      />
    </div>
  );
}

export default App;

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@hisam

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setState Callback in a Functional Component

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