The version attribute is used to indicate what specification a SVG document conforms to. It is only allowed on the root <svg> element. It is purely advisory and has no influence on rendering or processing.

The viewBox attribute defines the position and dimension, in user space, of an SVG viewport.

The lastIndex data property of a RegExp instance specifies the index at which to start the next match.

The String.raw() static method is a tag function of template literals. This is similar to the r prefix in Python, or the @ prefix in C# for string literals. It's used to get the raw string form of template literals — that is, substitutions (e.g. ${foo}) are processed, but escape sequences (e.g. \n) are not.

The catch() method of Promise instances schedules a function to be called when the promise is rejected. It immediately returns an equivalent Promise object, allowing you to chain calls to other promise methods. It is a shortcut for Promise.prototype.then(undefined, onRejected).

The then() method of Promise instances takes up to two arguments: callback functions for the fulfilled and rejected cases of the Promise. It immediately returns an equivalent Promise object, allowing you to chain calls to other promise methods.

The toLocaleString() method of Date instances returns a string with a language-sensitive representation of this date in the local timezone. In implementations with Intl.DateTimeFormat API support, this method simply calls Intl.DateTimeFormat.

The [@@iterator]() method of Array instances implements the iterable protocol and allows arrays to be consumed by most syntaxes expecting iterables, such as the spread syntax and for...of loops. It returns an array iterator object that yields the value of each index in the array.

Groups group multiple patterns as a whole, and capturing groups provide extra submatch information when using a regular expression pattern to match against a string. Backreferences refer to a previously captured group in the same regular expression.

This page provides an overall cheat sheet of all the capabilities of RegExp syntax by aggregating the content of the articles in the RegExp guide. If you need more information on a specific topic, please follow the link on the corresponding heading to access the full article or head to the guide.