The JavaScript warning "unreachable code after return statement" occurs when using an expression after a return statement, or when using a semicolon-less return statement but including an expression directly after.

The vert-origin-y attribute indicates the y-coordinate in the font coordinate system of the origin of a glyph to be used when drawing vertically oriented text.

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

The text-anchor attribute is used to align (start-, middle- or end-alignment) a string of pre-formatted text or auto-wrapped text where the wrapping area is determined from the inline-size property relative to a given point.

The JavaScript exception "missing = in const declaration" occurs when a const declaration was not given a value in the same statement (like const RED_FLAG;). You need to provide one (const RED_FLAG = "#ff0").

The x-height attribute indicates the height of lowercase glyphs in the font within the font coordinate system.

The requiredFeatures attribute takes a list of feature strings, with the individual strings separated by white space. It determines whether or not all of the named features are supported by the browser; if all of them are supported, the attribute evaluates to true end the element is rendered; otherwise, the attribute evaluates to false and the current element and its children are skipped and thus will not be rendered. This provides a way to design SVG that gracefully falls back when features aren't available.

The RegExp object is used for matching text with a pattern.

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

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.