A lookbehind assertion "looks behind": it attempts to match the previous input with the given pattern, but it does not consume any of the input — if the match is successful, the current position in the input stays the same. It matches each atom in its pattern in the reverse order.

A literal character specifies exactly itself to be matched in the input text.

The panose-1 attribute indicates the Panose-1 number of a font face.

The k3 attribute defines one of the values to be used within the arithmetic operation of the <feComposite> filter primitive.

The typeof operator returns a string indicating the type of the operand's value.

The unsigned right shift (>>>) operator returns a number whose binary representation is the first operand shifted by the specified number of bits to the right. Excess bits shifted off to the right are discarded, and zero bits are shifted in from the left. This operation is also called "zero-filling right shift", because the sign bit becomes 0, so the resulting number is always positive. Unsigned right shift does not accept BigInt values.

The lang attribute specifies the primary language used in contents and attributes containing text content of particular elements.

The let declaration declares re-assignable, block-scoped local variables, optionally initializing each to a value.

The name attribute specifies either the name of a color profile or a font face.

The try...catch statement is comprised of a try block and either a catch block, a finally block, or both. The code in the try block is executed first, and if it throws an exception, the code in the catch block will be executed. The code in the finally block will always be executed before control flow exits the entire construct.