How is it possible to send a (copy of) function from my main thread to my worker?
Whenever I try: worker.postMessage({data, func: (data) => data), firefox gives me an error message: DataCloneError: The object could not be cloned.
As for Chrome, the message differ, but the error still occur: Uncaught DOMException: Failed to execute 'postMessage' on 'Worker': An object could not be cloned.
Yes, it is possible, I did that, and better than that I can create web workers without js files, just using Blob files generated with javascript code.
setInterval(()=>{console.log("non bloked " + Math.random())}, 900)
console.log("starting blocking code in Worker")
console.time("blocked")
genericWorker(window, ["blockCpu", function (block){
block(10000) //This blockCpu function is defined below
return `\n\nbla ${123123*2312} bla \n` //This is catched in the resolved promise
}]).then(function (result){
console.timeEnd("blocked")
console.log("End of blocking code", result)
})
.catch(function(error) { console.log(error) })
/* A Web Worker that does not use a File, it create that from a Blob
@cb_context, The context where the callback functions arguments are, ex: window
@cb, ["fn_name1", "fn_name2", function (fn1, fn2) {}]
The callback will be executed, and you can pass other functions to that cb
*/
function genericWorker(cb_context, cb) {
return new Promise(function (resolve, reject) {
if (!cb || !Array.isArray(cb))
return reject("Invalid data")
var callback = cb.pop()
var functions = cb
if (typeof callback != "function" || functions.some((fn)=>{return typeof cb_context[fn] != "function"}))
return reject(`The callback or some of the parameters: (${functions.toString()}) are not functions`)
if (functions.length>0 && !cb_context)
return reject("context is undefined")
callback = fn_string(callback) //Callback to be executed
functions = functions.map((fn_name)=> { return fn_string( cb_context[fn_name] ) })
var worker_file = window.URL.createObjectURL( new Blob(["self.addEventListener('message', function(e) { var bb = {}; var args = []; for (fn of e.data.functions) { bb[fn.name] = new Function(fn.args, fn.body); args.push(fn.name)}; var callback = new Function( e.data.callback.args, e.data.callback.body); args = args.map(function(fn_name) { return bb[fn_name] }); var result = callback.apply(null, args) ;self.postMessage( result );}, false)"]) )
var worker = new Worker(worker_file)
worker.postMessage({ callback: callback, functions: functions })
worker.addEventListener('error', function(error){ return reject(error.message) })
worker.addEventListener('message', function(e) {
resolve(e.data), worker.terminate()
}, false)
//From function to string, with its name, arguments and its body
function fn_string (fn) {
var name = fn.name, fn = fn.toString()
return { name: name,
args: fn.substring(fn.indexOf("(") + 1, fn.indexOf(")")),
body: fn.substring(fn.indexOf("{") + 1, fn.lastIndexOf("}"))
}
}
})
}
//random blocking function
function blockCpu(ms) {
var now = new Date().getTime();
var result = 0
while(true) {
result += Math.random() * Math.random();
if (new Date().getTime() > now +ms)
return;
}
}
Not tested this yet, but it seems that from the spec, only objects that can be send to a Worker are "Transferable" objects: https://developer.mozilla.org/en-US/docs/Web/API/Transferable
I found some examples, in the first one the process is not detailled, but i'm guessing he uses a kind or URL encode, for an object, it can be converted to JSON like in the second example.
How to pass functions to JavaScript Web Worker
Passing objects to a web worker
I have to do this too in a couple of days, i can keep updated with what i have that will be tested..
