I have created a proper benchmark for that on jsperf. Depending on the browser, WebWorker approach is 85-95% slower than a raw ajax call.
Notes:
- since network response time can be different for each request, I’m testing only
new XMLHttpRequest()andJSON.parse(jsonString);. There are no real AJAX calls being made. - WebWorker setup and teardown operations are not being measured
- note that I’m testing a single request, results for webworker approach may be better for multiple simultaneous requests
- Calvin Metcalf explained to me that comparing sync and async on jsperf won’t give accurate results and he created another benchmark that eliminates async overhead. Results still show that WebWorker approach is significantly slower.
- From the Reddit discussion I learned that data passed between the main page and WebWorker are copied and have to be serialized in the process. Therefore, using WebWorker for parsing only doesn’t make much sense, data will have to be serialized and deserialized anyway before you can use them on the main page.