'Uncaught Error: DATA_CLONE_ERR: DOM Exception 25' thrown by web worker

thatmiddleway picture thatmiddleway · Sep 21, 2011 · Viewed 16.2k times · Source

So I'm creating a web worker:

var arrayit = function(obj) {
  return Array.prototype.slice.call(obj);
};
work = arrayit(images);
console.log(work);
//work = images.push.apply( images, array );
// Method : "load+scroll"
var worker = new Worker('jail_worker.js');
worker.postMessage(work)
worker.onmessage = function(event) {
  console.log("Worker said:" + event.data);
};

Here's what images is:

$.jail.initialStack = this;
// Store the selector into 'triggerEl' data for the images selected
this.data('triggerEl', (options.selector) ? $(options.selector) : $window);
var images = this;

I think my problem has something to do with this:

http://dev.w3.org/html5/spec/Overview.html#safe-passing-of-structured-data

How can I get around this? as you can see, I tried slicing the host object into a real array, but that didn't work.

Here's a link to the file I'm hacking on:

https://github.com/jtmkrueger/JAIL

UPDATE--------------------------------------------------

This is what I had to do based on the accepted answer from @davin:

var arrayit = function(obj) {
  return Array.prototype.slice.call(obj);
};
imgArray = arrayit(images);
work = _.map(images, function(i){ return i.attributes[0].ownerElement.outerHTML; });

var worker = new Worker('jail_worker.js');
worker.postMessage(work)
worker.onmessage = function(event) {
  console.log("Worker said:" + event.data);
};

NOTE: I used underscore.js to assure compatibility.

Answer

davin picture davin · Sep 22, 2011

The original exception was most likely thrown because you tried passing a host object to the web worker (most likely a dom element). Your subsequent attempts don't throw the same error. Remember two key points: there isn't shared memory between the different threads, and the web workers can't manipulate the DOM.

postMessage supports passing structured data to threads, and will internally serialise (or in some other way copy the value of the data recursively) the data. Serialising DOM elements often results in circular reference errors, so your best bet is to map the object you want serialised and extract relevant data to be rebuilt in the web worker.