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

The JavaScript exception "invalid regexp group" occurs when the sequence (? does not start a valid group syntax. Recognized group syntaxes that start with (? include:

The JavaScript exception "can't set prototype of this object" occurs when attempting to set the prototype of an object, but the object's prototype is frozen, either by being a built-in immutable prototype object, or by being non-extensible.

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 limitingConeAngle attribute represents the angle in degrees between the spot light axis (i.e., the axis between the light source and the point to which it is pointing at) and the spot light cone. So it defines a limiting cone which restricts the region where the light is projected. No light is projected outside the cone.

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 JavaScript exception "cyclic object value" occurs when object references were found in JSON. JSON.stringify() doesn't try to solve them and fails accordingly.

The repeatCount attribute indicates the number of times an animation will take place.

The JavaScript exception "import declarations may only appear at top level of a module" occurs when an import declaration is not at the top level of a module. This might be because the import declaration is nested in other constructs (functions, blocks, etc.), or more often because the current file is not treated as a module.

JavaScript is a prototype-based language — an object's behaviors are specified by its own properties and its prototype's properties. However, with the addition of classes, the creation of hierarchies of objects and the inheritance of properties and their values are much more in line with other object-oriented languages such as Java. In this section, we will demonstrate how objects can be created from classes.