New texts look nice. Two comments...
- XMLHttpRequest.send() is a good example, but as we go through multiple states and invokes onreadystatechange multiple times, I prefer not just quoting "onreadystatechange" but point the one-and-done aspect of XHR by using phrase like "which triggers onreadystatechange with readyState of DONE" - Could you please refrain from pointing the streams API or list both in the doc until we finish the discussion now we have?
