Undefined variable as function argument javascript

Question

I\'ve looked a fair bit, so pardon me if this has already been answered.

I\'m also curious as to what the actual term is called; Is it \"Ambiguous\" for the type of argu

Answer 1

A completely undeclared variable can't be passed in JS; you can only pass declared variables or undeclared properties of other variables.

In other words:

var a; // you can do _.defined(a)
var a = undefined; // you can do _.defined(a)
a.b; // you can do _.defined(a.b), even though we never defined b