Why does not Chrome allow Web Workers to be run in JavaScript?

4
votes

If I try to use web workers through a JavaScript file, Chrome throws an error -

Uncaught SecurityError: Failed to create a worker: script at '(path)/worker.js' cannot be accessed from origin 'null'.

But it allows them if we use directly through the HTML.

The answer on Chrome can't load web worker says Chrome doesn't let you load web workers when running scripts from a local file.

Why doesn't chrome allow web workers to run locally?

Web Workers work completely fine in Firefox, Safari and in Edge

2
javascripthtmlgoogle-chromeweb-worker
web workers have been supported by chrome since version 4.00, perhaps share your code? I suspect it's access to worker.js that's the problem. - Jim
Are your application running http (http://, https://) or streight from the file system (file://)? - Morten Olsen

2 Answers

8
votes

This question was already asked. The workers should work in HTML files opened from disk as long as you use relative path. However, if chrome implements this correctly has been disputed.

I advise that you try to use relative path in your scripts:

new Worker("./scripts/worker.js");

If that doesn't work, see this workaround: https://stackoverflow.com/a/33432215/607407

Specifically, load worker as a function, then convert the function to string:

function worker_function() {
    // all worker code here
}
var worker = new Worker(URL.createObjectURL(new Blob(["("+worker_function.toString()+")()"], {type: 'text/javascript'})));
1
votes
var cblock=`

function workerFunc(e){

    console.info('Hello World!',e.data.msg)
    postMessage({msg:'Complete!'})
}

addEventListener('message',workerFunc)
`    
var a=new Worker(URL.createObjectURL(new Blob( [cblock], {type:'text/javascript'} )))    
a.onmessage=function(e){ console.info('My worker called!',e.data.msg) }    
a.onerror=function(e){ console.info( JSON.stringify(e,' ',2) ) }    
a.postMessage({ msg:'Chrome WebWorkers work!' }) 

// Hello World! Chrome WebWorkers work!
// My worker called! Complete!