Private elements are counterparts of the regular class elements which are public, including class fields, class methods, etc. Private elements get created by using a hash # prefix and cannot be legally referenced outside of the class. The privacy encapsulation of these class elements is enforced by JavaScript itself. The only way to access a private element is via dot notation, and you can only do so within the class that defines the private element.

The JavaScript exceptions thrown by JSON.parse() occur when string failed to be parsed as JSON.

The JavaScript exception "missing ) after condition" occurs when there is an error with how an if condition is written. It must appear in parenthesis after the if keyword.

The patternUnits attribute indicates which coordinate system to use for the geometry properties of the <pattern> element.

The JavaScript strict mode-only exception "0-prefixed octal literals are deprecated; use the "0o" prefix instead" occurs when deprecated octal literals (0 followed by digits) are used.

A unicode character class escape is a kind of character class escape that matches a set of characters specified by a Unicode property. It's only supported in Unicode-aware mode. When the v flag is enabled, it can also be used to match finite-length strings.

The get syntax binds an object property to a function that will be called when that property is looked up. It can also be used in classes.

The JavaScript exception "is not a constructor" occurs when there was an attempt to use an object or a variable as a constructor, but that object or variable is not a constructor.

The JavaScript exception "invalid property name in regular expression" or "invalid class property name in regular expression" occurs when the \p and \P Unicode character class escapes are not followed by a valid Unicode property name and/or value.

The media attribute specifies a media query that must be matched for a style sheet to apply.