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 addition assignment (+=) operator performs addition (which is either numeric addition or string concatenation) on the two operands and assigns the result to the left operand.

The <defs> SVG element is used to store graphical objects that will be used at a later time. Objects created inside a <defs> element are not rendered directly. To display them you have to reference them (with a <use> element for example).

The conditional (ternary) operator is the only JavaScript operator that takes three operands: a condition followed by a question mark (?), then an expression to execute if the condition is truthy followed by a colon (:), and finally the expression to execute if the condition is falsy. This operator is frequently used as an alternative to an if...else statement.

The <fePointLight> SVG filter primitive defines a light source which allows to create a point light effect. It that can be used within a lighting filter primitive: <feDiffuseLighting> or <feSpecularLighting>.

The <animateTransform> SVG element animates a transformation attribute on its target element, thereby allowing animations to control translation, scaling, rotation, and/or skewing.

The eval() function evaluates JavaScript code represented as a string and returns its completion value. The source is parsed as a script.

The <feMorphology> SVG filter primitive is used to erode or dilate the input image. Its usefulness lies especially in fattening or thinning effects.

The <use> element takes nodes from within the SVG document, and duplicates them somewhere else. The effect is the same as if the nodes were deeply cloned into a non-exposed DOM, then pasted where the use element is, much like cloned template elements.

The <feDiffuseLighting> SVG filter primitive lights an image using the alpha channel as a bump map. The resulting image, which is an RGBA opaque image, depends on the light color, light position and surface geometry of the input bump map.