Event Objects!

Goals:

Process information about events using event objects
Explore the keypress and keyup events

Coding Snippets:

Event listeners automatically pass information about each event to the event handler, in the form of an event object
Access the event object by adding a single argument to the event handler. Common names for this argument are e, evt, and event.
Event objects have many other properties besides key, some of which are explored below.

Math and Computer Concepts:

The key event object's keyCode property provides a numeric value representing that key (similar to ASCII); the shiftKey, metaKey, ctrlKey, and altKey properties use boolean values to record the status of modifier keys at the time of the event; and the timeStamp property records how many milliseconds elapsed since the program started when the event fires.
keypress differs from keydown primarily in that the value of its key property is case sensitive. There are additional, more nuanced differences too, such as that the keypress event doesn't fire for keystrokes that don't produce visible output on the screen (e.g., shift or control ) and only keyup events fire for the delete key.

Activities:

Save each of the following in a folder called EventObjects.

SingleBindingMover: Make use of the keydown event object to create a program that allows the user to control a sprite using arrow keys. This program should contain only one call to the keydown event binding function.

KeyEventNuances: Explore the differences between the keydown, keypress, and keyup events. Write a simple script that uses the three key event binding functions to report the key, keyCode, and timeStamp properties.
Code a TypingTest program that tests how many letters you can correctly type in a given amount of time. Use keypress events to facilitate verifying that the typist correctly types upper and lower case letters. Measure time elapsed using the event object's timeStamp property (do not use Date objects).

Compose a Piano program using the tone function. Recall that tone 'A',2 causes the 'A' note to be played for two seconds; a subsequent call to tone 'A',0 silences that note. Use a single call to keydown to bind keystrokes of the keys on your computer to calls to tone to play musical notes. Similarly, use a single call to keyup to bind the release of those keys to calls to tone to make the notes stop playing.