The opacity attribute specifies the transparency of an object or of a group of objects, that is, the degree to which the background behind the element is overlaid.

Method definition is a shorter syntax for defining a function property in an object initializer. It can also be used in classes.

The extends keyword is used in class declarations or class expressions to create a class that is a child of another class.

The async function declaration creates a binding of a new async function to a given name. The await keyword is permitted within the function body, enabling asynchronous, promise-based behavior to be written in a cleaner style and avoiding the need to explicitly configure promise chains.

The divisor attribute specifies the value by which the resulting number of applying the kernelMatrix of a <feConvolveMatrix> element to the input image color value is divided to yield the destination color value.

The mode attribute defines the blending mode on the <feBlend> filter primitive.

The JavaScript exception "must call super constructor before using 'this' in derived class constructor" occurs when the super() is not called for a given derived class constructor, and the derived constructor tries to access the value of this, or the derived constructor has already returned and the return value is not an object.

The keySplines attribute defines a set of Bézier curve control points associated with the keyTimes list, defining a cubic Bézier function that controls interval pacing.

Below, you'll find a list of errors which are thrown by JavaScript. These errors can be a helpful debugging aid, but the reported problem isn't always immediately clear. The pages below will provide additional details about these errors. Each error is an object based upon the Error object, and has a name and a message.

The markerWidth attribute represents the width of the viewport into which the <marker> is to be fitted when it is rendered according to the viewBox and preserveAspectRatio attributes.