Classes often start in uppercase letters, while instances start with lowercase letters. This is a throwback of the general Python and Ruby practice of having constant names start with uppercase letters.
// Classes:
Photo
Album
Author
// Instances:
photo
myAlbum
For names with multiple words, JavaScript often calls for CamelCase. Using underscores are discouraged in JavaScript.
// Good (CamelCase):
PhotoAlbum
albumCover
// Avoid (under_scores):
photo_album
album_cover