Over my head

Events like mouse clicks and keystrokes are handled in a single dedicated thread.

If the handling JavaScript, which also runs in its own thread, is unresponsive, the browser remains responsive, but eventually willl inform the user of the problem and give them the option of cancelling the handler!

This means that long running client side code cannot be executed without implementing a continuation style approach.

Example 1
function clickHandler() {<br />process1();<br />process2();<br />process3();<br />}<br />could be replaced with:
Example 2
function longRunningProcess() {<br />runProcess1();<br />}<br /><br />function clickHandler() {<br />process1();<br />setTimeout(runProcess2(), 10);<br />}<br /><br />function runProcess2() {<br />process2();<br />setTimeout(runProcess3(), 10);<br />}<br /><br />function runProcess3() {<br />process3();<br />}<br />

This is horrible. However, the javascript library Narrative enables blocking capabilities for asynchronous event callbacks. This makes asynchronous code more readable.

So, it will convert the following code into Example 2:

<br />function longRunningProcess() {<br />process1();<br />sleep(10);<br />process2();<br />sleep(10);<br />process3();<br />}<br />
Fortunately, it is rare that the client code should ever have to execute long processes.