JavaScript optional parameter

Note the difference between parameters and arguments: Function parameters are the names listed in the function’s definition. Function arguments are the real values passed to the function.

The parameters, in a function call, are the function’s arguments . JavaScript arguments are passed by value: The function only gets to know the values, not the argument’s locations. If a function changes an argument’s value, it does not change the parameter’s original value.

A method that contains optional parameters does not force to pass arguments at calling time . It means we call method without passing the arguments. The optional parameter contains a default value in function definition. If we do not pass optional argument value at calling time, the default value is used.

Optional parameters are defined at the end of the parameter list, after any required parameters . If the caller provides an argument for any one of a succession of optional parameters, it must provide arguments for all preceding optional parameters.

Optional parameters are defined at the end of the parameter list, after any required parameters . If the caller provides an argument for any one of a succession of optional parameters, it must provide arguments for all preceding optional parameters.

The parameters, in a function call, are the function’s arguments . JavaScript arguments are passed by value: The function only gets to know the values, not the argument’s locations. If a function changes an argument’s value, it does not change the parameter’s original value.