xhr.upload.addEventListener加载具有空的xhr.responseText

Question

xhr.open('put',url,false)
xhr.upload.addEventListener('load',function(e){alert(xhr.responseText)},false)

Why is xhr.responseText empty? When using xhr.onreadystatechange 4 xhr.responseText has data?

Answer 1

What Gert is trying to say is that you have to add the event listener to the xhr object, not xhr.upload . I'm not entirely sure why and the spec isn't exactly clear. It isn't anything to do with asynchronous requests which are the default anyway.

Instead of:

xhr.upload.addEventListener('load', function(e){ alert(xhr.responseText); }, false);

You must do:

xhr.addEventListener('load', function(e){ alert(xhr.responseText); }, false);

Answer 2

(My old answer maybe wrong see new answer Timmmm)

I needed to set XMLHttpRequest asynchronously for it to work.

xhr.open('put',url,true)

xhr.addEventListener('load',function(e){alert(xhr.response)},false)