事件处理程序中的setTimeout似乎不触发

Question

Am aware that not all setTimout tasks put on the queue are actually fired (thanks a post by bobnice on this). Yet I can't understand why it would not be reached in this case :

I add the following event handler to an anchor link (via addEventListener( 'click', ... ) to experiment with so-called "in-flight event modification" :

var f = function(e) {  
    e.preventDefault(); 
    e.stopPropagation(); // capture first event
    e2 = new MouseEvent("click",{metaKey:true}); // create second event where we hold meta
    e.target.removeEventListener('click', f, false); // remove this handler so no stackoverflow
    e.target.dispatchEvent(e2); // dispatch second event, a "modified" first event.
};

Works fine.

However, an earlier version had this :

setTimeout( 0, function () {
    e.target.dispatchEvent(e2); // dispatch second event, a "modified" first event.
});

From within the handler (as a debugging patch to try to avoid stackoverflow when I couldn't get the removeEventListener to work -- I had neglected to assign my function f to a variable).

Why would this setTimeout not execute? In my handful of tests, it never once executed the dispatching of the second event from within the listener for the first event.

Clearly, the setTimeout puts the execution context of dispatchEvent outside of the stack frame for the function f , as f returns before dispatchEvent fires.

Or, rather, doesn't fire.

I would like to understand exactly why it didn't fire in this previous version of the code.

Answer 1

The timeout delay for setTimeout should be the second argument, not the first! That's why it didn't fire.