The var statement declares function-scoped or globally-scoped variables, optionally initializing each to a value.

The while statement creates a loop that executes a specified statement as long as the test condition evaluates to true. The condition is evaluated before executing the statement.

The JavaScript exception "precision is out of range" occurs when a number that's outside of the allowed range was passed into toExponential, toFixed, or toPrecision.

The Object type represents one of JavaScript's data types. It is used to store various keyed collections and more complex entities. Objects can be created using the Object() constructor or the object initializer / literal syntax.

The throw statement throws a user-defined exception. Execution of the current function will stop (the statements after throw won't be executed), and control will be passed to the first catch block in the call stack. If no catch block exists among caller functions, the program will terminate.

The hanging attribute indicates the alignment coordinate for glyphs to achieve hanging baseline alignment for horizontally oriented glyph layouts. The value is an offset in the font coordinate system.

A WeakMap is a collection of key/value pairs whose keys must be objects or non-registered symbols, with values of any arbitrary JavaScript type, and which does not create strong references to its keys. That is, an object's presence as a key in a WeakMap does not prevent the object from being garbage collected. Once an object used as a key has been collected, its corresponding values in any WeakMap become candidates for garbage collection as well — as long as they aren't strongly referred to elsewhere. The only primitive type that can be used as a WeakMap key is symbol — more specifically, non-registered symbols — because non-registered symbols are guaranteed to be unique and cannot be re-created.

The horiz-origin-x attribute indicates the x-coordinate in the font coordinate system of the origin of a glyph to be used when drawing horizontally oriented text.

The markerUnits attribute defines the coordinate system for the markerWidth and markerHeight attributes and the contents of the <marker>.

The Generator object is returned by a generator function and it conforms to both the iterable protocol and the iterator protocol.