jQuery / AJAX并发访问全局变量

Question

I'm writing some jQuery code that performs a plain ajax call. I've a global Javascript variable that I need to increase thread-safely with every call. If this was Java, I would use synchronized but this is not the case :-)

Here's a code snippet:

var myval;

function myFunc()
{
    $.ajax({
        url: myurl,
        type: 'GET',
        data: { ...my data... },
        success: function()
        {
            myval++;
        }
    });
}

Given that myFunc() is associated with a click event, how can I be sure that myvar is always safely/consistently increased? I know I could maybe use async: false , but I'd prefer to avoid it. I'm not even sure it would work that way.

Thanks for any help!

Answer 1

There's no problem - JS doesn't suffer atomicity problems since there are no (user-visible) threads[*]

Nothing happens in JS except in response to an event or initial script load. It's impossible for a piece of code to misread myval during an increment, because the entire success callback must complete before any other event handling code can start.

[*] Yes, there's WebWorkers, but they use message passing not variable sharing.