JavaScript function parameters

Assigning an initial value to a parameter
There is no overloaded concept in JavaScript, but the parameters of the functions in JavaScript are optional, and if a parameter is written less, it will be replaced by undefined.

eg

function Add (A, b) {return a + B;} plus (5); NaN

Here Add (5) is equivalent to add (5, undefined), and the result of 5 + undefined is Nan.

Convert arguments to arrays
The predefined variable in the function arguments is not a true array, but an array-like object.
It has the length property, but there is no slice, push, sort, and so on, so how do you make arguments have the functions of these arrays?
So how do you make arguments into a real array?

function args () {return [].slice.call (arguments, 0);} args (2, 5, 16); [2, 5, 16]

JavaScript function parameters