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How to block on asynchronous functions in JavaScript

I need to write a function in JavaScript, which returns a state from calling an asynchronous function. However, the caller only receives the value and no callback function is to be provided. I tried something like:

function getState() {
 var ret = null;
 asyncCall("request",
 function() { ret = "foo"; } // callback
 );
 while (ret === null)
 ; // block on the asynchronous call
 return ret;
}

However, the loop is never going to end...

Any ideas? Thank you.

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  • It's something like a library since I am working across several platforms. And the rest of the code needs to wait for this special piece of information. No synchronous substitution is provided. Commented Dec 3, 2010 at 13:36
  • 2
    @Šime: So you mean asynchronous calls could infect all other code calling it? I just want to know if there is a way to block on these async calls. Commented Dec 3, 2010 at 13:40
  • 1
    @ryanli: There is no way to block async call unless you A: rewrite the async call to be synchronous or B: rewrite your code to work in an asynchronous environment. In javascript it is considered best practice to do B since 1999. Commented Dec 3, 2010 at 13:50

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