Modifying a variable in a forEach loop

[Paul Carey]

Hi

I would have expected the following to change the value of a, but just
discovered it doesn't.

var forEach = function () {
var a = "a";
[a].forEach(functi on (v, i) {
console.log("v= " + v);
v = i;
console.log("v= " + v);
});
console.log("a= " + a);
};

The output is:
v=a
v=0
a=a

I'm not really sure why, I'd be very grateful if someone could
explain.
Thanks

Paul

[slebetman]

Re: Modifying a variable in a forEach loop

On Oct 7, 7:15 pm, Paul Carey <paul.p.ca...@g mail.comwrote:

Hi
>
I would have expected the following to change the value of a, but just
discovered it doesn't.
>
var forEach = function () {
var a = "a";
[a].forEach(functi on (v, i) {
console.log("v= " + v);
v = i;
console.log("v= " + v);
});
console.log("a= " + a);
>
};
>
The output is:
v=a
v=0
a=a
>
I'm not really sure why, I'd be very grateful if someone could
explain.

In javascript, plain numbers and strings are passed by value. Only
objects are passed by reference. If we modify your code slightly
you'll see the expected behavior:

var forEach = function () {
var a = {value:"a"};
[a].forEach(functi on (v, i) {
console.log("v" ,v);
v.value = i;
console.log("v" ,v);
});
console.log("a" ,a);
};

output:
v Object value=a
v Object value=0
a Object value=0

[dhtml]

Re: Modifying a variable in a forEach loop

slebetman wrote:

On Oct 7, 7:15 pm, Paul Carey <paul.p.ca...@g mail.comwrote:

>
In javascript, plain numbers and strings are passed by value. Only
objects are passed by reference. If we modify your code slightly
you'll see the expected behavior:
>

Actually, object references are passed by value.

Garrett