Returns the number of style declarations in a css declaration block. Stricten variable redeclaration checks to also report even if the declared types of the. The const declaration creates a readonly reference to a value. Of course you may try to call the copy constructor, but there is no any sense. An explanation of why the name let was chosen can be found here. Lions at the zoo zoos allow for safely viewing dangerous wild animals like lions. The current implementation of const is a mozillaspecific extension and is not part of ecmascript 5.