title: What does the onload method do in Json's xmlHttprequest object
body: <p>I am taking a crash course on java script for this course <a href="https://www.udacity.com/course/viewer#!/c-cs255/l-52473341/e-66738295/m-67610028" rel="nofollow">https://www.udacity.com/course/viewer#!/c-cs255/l-52473341/e-66738295/m-67610028</a>, 
  and I am really not sure what does an onload method of xmlHttprequest object does. I did google, but all the answers seems so advance and nothing relevant to the stuff I am learning. The course ended so no one will respond to my questions. Thanks, </p>