Javascript function that returns the YouTube ID when given a YouTube video URL.

get_youtube_id_from_url.js

/**
 * Function that returns the YouTube ID when given the YouTube URL.
 *
 * @param url string
 * @return int|null
 */
function get_youtube_id_from_url(url) {
    const regExp = /^.*(youtu.be\/|v\/|u\/\w\/|embed\/|watch\?v=|&v=)([^#&?]*).*/;
    const match = url.match(regExp);

    return (match && match[2].length === 11)
        ? match[2]
        : null;
}