Types as Arguments
Learn JS Fundamentals to jQuery & Pure DOM Scriptingwhenever a function is created in memory it has a PROTOTYPE property that points to an object
var sum = function(x,y){
return (++x) + (++y.val);
};
a = 1;
b = {val:2};
c = sum(a,b);
inside sum(a,b) the x is a primitive so it's passed by value (it will pass a copy a) but y will be passed by reference so it will point to b this is why
a will stay as 1 but b.val will increment to 2.note: in JavaScript primitives cannot be mutated - if you change it will take another place in memory
Call objects know about their parent call objects - this is how closures workCall objects are objects (like
window or global) (it holds variables, this reference, etc.)Every time you call a function a new call object is created
So if a function returns another function and it's called several times, every time a new function is created. This is wgy
c2() fill be 1 here:
var counter = function () {
var count = 0;
return function () {
return ++count;
}
}
var ca1 = counter();
c1(); // 1
c1(); // 2
var c2 = counter();
c2(); // 1