The void operator evaluates the given expression and then returns undefined.

The boolean type.

The JavaScript exception "invalid regexp group" occurs when the sequence (? does not start a valid group syntax. Recognized group syntaxes that start with (? include:

The dur attribute indicates the simple duration of an animation.

The try...catch statement is comprised of a try block and either a catch block, a finally block, or both. The code in the try block is executed first, and if it throws an exception, the code in the catch block will be executed. The code in the finally block will always be executed before control flow exits the entire construct.

The font-stretch attribute indicates the desired amount of condensing or expansion in the glyphs used to render the text.

The end attribute defines an end value for the animation that can constrain the active duration.

A lookbehind assertion "looks behind": it attempts to match the previous input with the given pattern, but it does not consume any of the input — if the match is successful, the current position in the input stays the same. It matches each atom in its pattern in the reverse order.

The image-rendering attribute provides a hint to the browser about how to make speed vs. quality tradeoffs as it performs image processing.

The RegExp object is used for matching text with a pattern.