event in a web worker + capture code example

Example 1: what is webworker

web worker
Web Workers are a mechanism to create a separate thread 
in parallel to your main JS program thread. 
can only communicate with each other through normal async events 
always abide by the event-loop one-at-a-time behavior 
required by run-to-completion.

Example 2: web worker multiple data

onmessage = function (e,f) {
    username = e.data.username;
    server_url = e.data.url;
}