The JavaScript exception "missing ] after element list" occurs when there is an error with the array initializer syntax somewhere. Likely there is a closing square bracket (]) or a comma (,) missing.

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

A backreference refers to the submatch of a previous capturing group and matches the same text as that group. For named capturing groups, you may prefer to use the named backreference syntax.

A word boundary assertion checks if the current position in the string is a word boundary. A word boundary is where the next character is a word character and the previous character is not a word character, or vice versa.

A 16-bit floating-point type (specifically, the “binary16” type defined in IEEE 754-2008).

The JavaScript exception "Invalid array length" occurs when specifying an array length that is either negative, a floating number or exceeds the maximum supported by the platform (i.e., when creating an Array or ArrayBuffer, or when setting the length property).

The fx attribute defines the x-axis coordinate of the focal point for a radial gradient.

The static import declaration is used to import read-only live bindings which are exported by another module. The imported bindings are called live bindings because they are updated by the module that exported the binding, but cannot be re-assigned by the importing module.

The id attribute assigns a unique name to an element.

JavaScript (JS) is a lightweight interpreted (or just-in-time compiled) programming language with first-class functions. While it is most well-known as the scripting language for Web pages, many non-browser environments also use it, such as Node.js, Apache CouchDB and Adobe Acrobat. JavaScript is a prototype-based, multi-paradigm, single-threaded, dynamic language, supporting object-oriented, imperative, and declarative (e.g., functional programming) styles.