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 JavaScript exception "property name __proto__ appears more than once in object literal" occurs when an object literal contains multiple occurrences of the __proto__ field, which is used to set the prototype of this new object.

The switch statement evaluates an expression, matching the expression's value against a series of case clauses, and executes statements after the first case clause with a matching value, until a break statement is encountered. The default clause of a switch statement will be jumped to if no case matches the expression's value.

The JavaScript exception "missing = in const declaration" occurs when a const declaration was not given a value in the same statement (like const RED_FLAG;). You need to provide one (const RED_FLAG = "#ff0").

The JavaScript strict mode-only exception "is read-only" occurs when a global variable or object property that was assigned to is a read-only property.

The JavaScript exception "invalid character in class in regular expression" occurs when a character appears in a v-mode character class but it's not allowed to appear literally.

The style attribute allows to style an element using CSS declarations. It functions identically to the style attribute in HTML.

The stemh attribute indicates the horizontal stem width of the font.

A character escape represents a character that may not be able to be conveniently represented in its literal form.

The path attribute has two different meanings, either it defines a text path along which the characters of a text are rendered, or a motion path along which a referenced element is animated.