The maskContentUnits attribute indicates which coordinate system to use for the contents of the <mask> element.

The JavaScript exception "return not in function" occurs when a return statement is called outside of a function.

The JavaScript exception "can't delete non-configurable array element" occurs when it was attempted to shorten the length of an array, but one of the array's elements is non-configurable.

The JavaScript exception "Unexpected '#' used outside of class body" occurs when a hash ("#") is encountered in an unexpected context, most notably outside of a class declaration. Hashes are valid at the beginning of a file as a hashbang comment, or inside of a class as part of a private field. You may encounter this error if you forget the quotation marks when trying to access a DOM identifier as well.

The stroke attribute is a presentation attribute defining the color (or any SVG paint servers like gradients or patterns) used to paint the outline of the shape;

The stroke-miterlimit attribute is a presentation attribute defining a limit on the ratio of the miter length to the stroke-width used to draw a miter join. When the limit is exceeded, the join is converted from a miter to a bevel.

The JavaScript strict mode-only exception "applying the 'delete' operator to an unqualified name is deprecated" occurs when variables are attempted to be deleted using the delete operator.

The r attribute defines the radius of a circle.

The specularConstant attribute controls the ratio of reflection of the specular lighting. It represents the ks value in the Phong lighting model. The bigger the value the stronger the reflection.

The JavaScript warning "Using //@ to indicate sourceURL pragmas is deprecated. Use //# instead" occurs when there is a deprecated source map syntax in a JavaScript source.