The in operator returns true if the specified property is in the specified object or its prototype chain.

The increment (++) operator increments (adds one to) its operand and returns the value before or after the increment, depending on where the operator is placed.

The pathLength attribute lets authors specify a total length for the path, in user units. This value is then used to calibrate the browser's distance calculations with those of the author, by scaling all distance computations using the ratio pathLength / (computed value of path length).

The break statement terminates the current loop or switch statement and transfers program control to the statement following the terminated statement. It can also be used to jump past a labeled statement when used within that labeled statement.

The export declaration is used to export values from a JavaScript module. Exported values can then be imported into other programs with the import declaration or dynamic import. The value of an imported binding is subject to change in the module that exports it — when a module updates the value of a binding that it exports, the update will be visible in its imported value.

The lighting-color attribute defines the color of the light source for lighting filter primitives.

The JSON.stringify() static method converts a JavaScript value to a JSON string, optionally replacing values if a replacer function is specified or optionally including only the specified properties if a replacer array is specified.

The hasOwnProperty() method of Object instances returns a boolean indicating whether this object has the specified property as its own property (as opposed to inheriting it).

The findLastIndex() method of Array instances iterates the array in reverse order and returns the index of the first element that satisfies the provided testing function. If no elements satisfy the testing function, -1 is returned.

A closure is the combination of a function bundled together (enclosed) with references to its surrounding state (the lexical environment). In other words, a closure gives you access to an outer function's scope from an inner function. In JavaScript, closures are created every time a function is created, at function creation time.