Java Reference
In-Depth Information
request("https://s3.amazo") },
api.addEventListener("click", function(){
request("http://ip.jsonte") }, false);
This calls the request() function when the button is clicked. This function is where the
Ajax request will happen. It accepts a URL as a parameter, which is where the request is
sent. Let's add this function to the end of the file:
scripts.js (excerpt)
function request(url) {
var xhr = new XMLHttpRequest();
xhr.onreadystatechange = function() {
if (xhr.readyState === 4 && xhr.status === 200) {
document.getElementById("output").innerHTML = xhr.
}"GET", url, true);
document.getElementById("output").innerHTML = "Waiting
response ...";
Inside this function, we create a new XMLHttpRequest object and then assign an
anonymous function to the onreadystatchange property. This checks the
readyState property to see if the request is complete (when the readyState property
is 4 ). Once complete it replaces the inner HTML of the output div with the response text.
The open() method sets up an asynchronous GET request to the URL provided (depend-
ing on which button was pressed) and then the request is sent. Last of all, we update the
output div with a message saying “Waiting for response ...” . This demon-
strates the asynchronous nature of an Ajax request because it will be shown before the re-
sponse. The text and HTML files take very little time to be shown after they're downloaded
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