Default function parameters allow formal parameters to be initialized with default values or undefined is passed. ECMAScript spec allows parameters without defaults after default parameters. Why? This ...

For functions in JavaScript you can define a default value for a parameter for handling the case where a parameter is not provided, falling back to the dafault.

providing a default value for one of them if only 2 are specified. My typical solution is to check the number of arguments passed to the function and reassign the named parameters as needed. I think ...