The JavaScript exception "can't redefine non-configurable property" occurs when it was attempted to redefine a property, but that property is non-configurable.

The indexOf() method of Array instances returns the first index at which a given element can be found in the array, or -1 if it is not present.

The type attribute is a generic attribute and it has different meaning based on the context in which it's used.

The Promise() constructor creates Promise objects. It is primarily used to wrap callback-based APIs that do not already support promises.

The y attribute defines a y-axis coordinate in the user coordinate system.

The v-hanging attribute indicates the alignment coordinate for glyphs to achieve hanging baseline alignment. The value is an offset in the font coordinate system relative to the glyph-specific vert-origin-x attribute.

The JavaScript exception "property is non-configurable and can't be deleted" occurs when it was attempted to delete a property, but that property is non-configurable.

The word-spacing attribute specifies spacing behavior between words.

The x2 attribute is used to specify the second x-coordinate for drawing an SVG element that requires more than one coordinate. Elements that only need one coordinate use the x attribute instead.

The enable-background attribute specifies how the accumulation of the background image is managed.