Introduction to React v2

Searching

This section will only be covered if we have additional time during the workshop.

Implementing Search for Movie List

Our current movie list will displays all movies. It would be nice if our user can filter the result by searching with key words. Let's implement that.

First of all, filtering result is usually done via backend as frontend application usually doesn't have all the data (if it is, it would be very slow to use your application).

Luckily, our current movies API supports search. Open a new browser tab with the following URL and you would see only Aquaman is in the movie list:

https://react-intro-movies.herokuapp.com/movies?q=aqua

The end part of the URL (q=aqua) is how we search the list. Providing different value (e.g. q=bumble) would returns you different results.

Passing Extra Parameter in Ajax Call

Update loadMovies function in api.js to accept a searchKey parameters:

js
export const loadMovies = searchKey =>
getAxios()
.then(axios =>
axios.default('https://react-intro-movies.herokuapp.com/movies', {
params: { q: searchKey },
})
)
.then(res => res.data);
  • axios accept a second parameter to customize the ajax call. params is an object that will be transformed to query string and append to the end of the ajax call.

Update useMovieData hook in app.js:

js
...
function useMovieData() {
...
const loadMoviesData = searchKey => {
setIsLoading(true);
loadMovies(searchKey).then(movieData => {
setMovies(movieData);
setIsLoading(false);
});
};
}
  • loadMoviesData accepts searchKey parameter now, which will be passed to loadMovies call.

Add an Input to Capture Search Key

Now we need to add an input to our App to capture searchKey.

jsx
function App() {
const [moviesShown, toggleShowMovies] = useToggle(false);
const { movies, isLoading, loadMoviesData } = useMovieData();
const { setName, setReleaseDate, setId, values } = useMovieForm();
const [isEdit, setIsEdit] = React.useState(false);
const [searchKey, setSearchKey] = React.useState('');
...
return (
...
{moviesShown && (
<BusyContainer isLoading={isLoading}>
<div className="field">
<input
value={searchKey}
onChange={ev => setSearchKey(ev.target.value)}
className="input"
placeholder="Search for movie..."
/>
</div>
<React.Suspense fallback={<span className="spinner" />}>
{movies.map(movie => (
<Movie
name={movie.name}
releaseDate={movie.releaseDate}
onClick={() => selectMovie(movie)}
key={movie.id}
/>
))}
</React.Suspense>
</BusyContainer>
)}
...
);
}
  • A new state searchKey is declared with initial value of ''.
  • An input is rendered with value and onChange set accordingly.

Make API call when searchKey change

Currently we can type our search key in the input, but that doesn't update the movie list. To do that, let's move the ajax call effects from useMovieData hook into App component:

js
...
function useMovieData() {
const [movies, setMovies] = React.useState([]);
const [isLoading, setIsLoading] = React.useState(true);
const loadMoviesData = searchKey => {
setIsLoading(true);
loadMovies(searchKey).then(movieData => {
setMovies(movieData);
setIsLoading(false);
});
};
// React.useEffect(loadMoviesData, []);
return {
movies,
isLoading,
loadMoviesData
};
}
...
function App() {
const [moviesShown, toggleShowMovies] = useToggle(false);
const { movies, isLoading, loadMoviesData } = useMovieData();
const { setName, setReleaseDate, setId, values } = useMovieForm();
const [isEdit, setIsEdit] = React.useState(false);
const [searchKey, setSearchKey] = React.useState('');
React.useEffect(() => loadMoviesData(searchKey), [searchKey]);
...
}

Now our movie list will be updated based on what we type! Done? Nope.

Debounce Effect

Our current code works, but it is unoptimal because we make an AJAX call for every keystroke. We need to "hold on" while user type, and only make the AJAX call after user stop typing.

To do that, let's create a file use-debounced-effect.js in src/hooks folder:

js
import React from 'react';
export const useDebouncedEffect = (effect, deps, timeout = 500) => {
React.useEffect(() => {
let cleanup;
const timerId = setTimeout(() => {
cleanup = effect();
}, timeout);
return () => {
clearTimeout(timerId);
if (typeof cleanup === 'function') cleanup();
};
}, deps);
};
  • In its essence, useDebouncedEffect hook works almost like useEffect hook, with the ability to limits the rate at which the effect can be called. It achieves this by waiting for a buffer time before calling the effect, and if the effect is invoked again before the buffer time finishes, it will cancel the previous call and restart the buffer again. It is conceptually similar to debounce of most utility libraries such as lodash and underscore.

In our App component, let's use useDebouncedEffect instead of useEffect hook:

js
...
import { useDebouncedEffect } from './hooks/use-debounced-effect';
...
function App() {
...
useDebouncedEffect(() => loadMoviesData(searchKey), [searchKey]);
...
}

Now when you try to search, it will on hold for half a second before start firing the AJAX call. :sunglasses:

Do It: Implement Search Movies Functionalities with Debounce

  1. Make the changes required to allow user to search movies.
  2. Verify that the movies is updated when you type to the input field.
  3. Add useDebouncedEffect hook and use it in your App.
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