React useState

Updated 27/03/2022

Returns a stateful value, and a function to update it.

JSX

Code example by Brian Holt.

import { useState } from "react";

const ANIMALS = ["bird", "cat", "dog", "rabbit", "reptile"];

const SearchParams = () => {
  const [animal, updateAnimal] = useState("");
  const [location, updateLocation] = useState("");
  const [breed, updateBreed] = useState("");
  const breeds = [];

  return (
    <div className="search-params">
      <form>
        <label htmlFor="location">
          Location
          <input
            id="location"
            value={location}
            placeholder="Location"
            onChange={(e) => updateLocation(e.target.value)}
          />
        </label>
        <label htmlFor="animal">
          Animal
          <select
            id="animal"
            value={animal}
            onChange={(e) => updateAnimal(e.target.value)}
            onBlur={(e) => updateAnimal(e.target.value)}
          >
            <option />
            {ANIMALS.map((animal) => (
              <option key={animal} value={animal}>
                {animal}
              </option>
            ))}
          </select>
        </label>
        <label htmlFor="breed">
          Breed
          <select
            disabled={!breeds.length}
            id="breed"
            value={breed}
            onChange={(e) => updateBreed(e.target.value)}
            onBlur={(e) => updateBreed(e.target.value)}
          >
            <option />
            {breeds.map((breed) => (
              <option key={breed} value={breed}>
                {breed}
              </option>
            ))}
          </select>
        </label>
        <button>Submit</button>
      </form>
    </div>
  );
};

export default SearchParams;

React.FC

Code example by Ibrahima Ndaw.

import * as React from "react";

export const App: React.FC = () => {
 const [counter, setCounter] = React.useState<number>(0)
 
 return (
    <div className="App">
      <h1>Result: { counter }</h1>
      <button onClick={() => setCounter(counter + 1)}>+</button>
      <button onClick={() => setCounter(counter - 1)}>-</button>
    </div>
  );
}

References

• https://reactjs.org/docs/hooks-reference.html#usestate