Javascript Function-Pointer Assignment

Question

Consider this javascript code:

var bar = function () { alert(\"A\"); }
var foo = bar;
bar = function () { alert(\"B\"); };
foo();

When runn

Answer 1

Those are not function pointers (and there are no pointers in JS natively). Functions in JS can be anonymous and are first class objects. Hence

function () { alert("A"); }

creates an anonymous function that alerts "A" on execution;

var bar = function () { alert("A"); };

assign that function to bar;

var foo = bar;

assign foo to bar, which is the function "A".

bar = function () { alert("B"); };

rebind bar to an anonymous function "B". This won't affect foo or the other function "A".

foo();

Call the function stored in foo, which is the function "A".

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Actually in languages where there are function points e.g. C it won't affect foo either. I don't know where you get the idea of getting "B" on reassignment.

void A(void) { printf("A\n"); }
void B(void) { printf("B\n"); }
typedef void(*fptr_t)(void);
fptr_t foo = A;
fptr_t bar = foo;
bar = B;
foo(); // should print "A"