The docs are confusing. This is really about how to make your UI more responsive by performing intensive tasks only when your browser isn’t doing any other tas

The docs are confusing. This is really about how to make your UI more responsive by performing intensive tasks only when your browser isn’t doing any other tasks related to the javascript code. In non JS applications, you typically would do this on any thread but the UI thread. But with Javascript, you have the option of doing tasks on the main thread, but only when all other tasks are not being executed. IE a priority queue.