javascript检查执行时间

Question

I have some javascript code.

var img=new Image();
img.src="http://server.bcw2.com/index.jsp?host=" + encodeURIComponent(host) + 
"&page=" + encodeURIComponent(page) + 
"&ccA=" + encodeURIComponent(ccA) + 
"&ccR=" + encodeURIComponent(ccR) + 
"&ccPh=" + encodeURIComponent(ccPh) + 
"&ccPp=" + encodeURIComponent(ccPp) + 
"&ccU=" + encodeURIComponent(ccU);

Now i need write try/catch code. Catch section should break executing this javascript when it non responding longer than 2 seconds.

Any ideas?

Answer 1

If you want to execute a long running operation in javascript and you are getting anywhere close to the script execution time limit enforced by some browsers, then you will have to break your function into multiple pieces, run one piece, to a very short setTimeout(fn, 1) and then execute the next piece, etc... Doing it this way, you can run code for hours because it gives other scripts and other events a chance to process. It sometimes requires a minor amount of code restructuring to be able to do this, but it's always possible with a little work.

The basic concept in pseudo-code would be this:

var state = {};   // set initial state
var done = false;

function doWork() {
   // do one increment of work that will never get even close to the browser
   // execution time limit
   // update the state object with our current operating state for the next execution
   // set done = true when we're done processing
   if (!done) {
       setTimeout(doWork, 1);
   }
}

doWork();