The Math namespace object contains static properties and methods for mathematical constants and functions.

The isFinite() function determines whether a value is finite, first converting the value to a number if necessary. A finite number is one that's not NaN or ±Infinity. Because coercion inside the isFinite() function can be surprising, you may prefer to use Number.isFinite().

The delete operator removes a property from an object. If the property's value is an object and there are no more references to the object, the object held by that property is eventually released automatically.

Symbol is a built-in object whose constructor returns a symbol primitive — also called a Symbol value or just a Symbol — that's guaranteed to be unique. Symbols are often used to add unique property keys to an object that won't collide with keys any other code might add to the object, and which are hidden from any mechanisms other code will typically use to access the object. That enables a form of weak encapsulation, or a weak form of information hiding.

The <metadata> SVG element adds metadata to SVG content. Metadata is structured information about data. The contents of <metadata> should be elements from other XML namespaces such as RDF, FOAF, etc.

The attributeName attribute indicates the name of the CSS property or attribute of the target element that is going to be changed during an animation.

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The stroke-dashoffset attribute is a presentation attribute defining an offset on the rendering of the associated dash array.

The startOffset attribute defines an offset from the start of the path for the initial current text position along the path after converting the path to the <textPath> element's coordinate system.

The JavaScript strict mode-only exception "setting getter-only property" occurs when there is an attempt to set a new value to a property for which only a getter is specified.