jQuery variable increment ++ not working in script

Question

I have this jQuery function that switches between different status messages (p elements) with ID's ranging from status_0 to status_5:

setTimeout(function() {
    var next_status;

    if (current_status < 5) {
        next_status = current_status++;
    } else {
        next_status = 0;
    }

    $(".status_visible").fadeOut("fast", function() {
        $("#status_"+next_status).fadeIn("fast");
    });

    //alert(next_status);

    change_status();
}, 10000);

My problem is that to start with, current_status definitely equals 0, but when it gets to my increment part, it comes out as 0 still! I tried this with a simple next_status = current_status + 1, which returned 01 instead of 1 (concatenated them), so I tried next_status = current_status++ and it returned 0 still.

Can anybody put me straight here please :)

In addition to the pre-incrementing operator suggested by Huang Tao, you could replace the entire if/else with next_status = ++current_status % 5 — user1106925
– user1106925, Commented Jul 16, 2012 at 2:55
@amnotiam: thanks for that, that's really helpful, and interesting. — TheCarver
– TheCarver, Commented Jul 16, 2012 at 3:56

Huang Tao · Accepted Answer · 2012-07-16 02:51:18Z

13

next_status = ++ current_status;

answered Jul 16, 2012 at 2:51

Huang Tao

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Ned Batchelder · Accepted Answer · 2012-07-16 02:53:23Z

1

The expression current_status++ means, "increment current_status, and evaluate to the old value of current_status," that is, use current_status, and then increment it after you note its value.

You want, ++current_status, which means, "increment current_status, and evaluate to the new value."

answered Jul 16, 2012 at 2:53

Ned Batchelder

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Spirit Walker · Accepted Answer · 2012-07-16 02:50:02Z

-1

is your timeout method "setTimeout" going to be called multiple times? If so , you need to pass your counter as a parameter with global scope, otherwise it will be reset each time.

answered Jul 16, 2012 at 2:50

Spirit Walker

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