How to get the response of XMLHttpRequest?

You can get it by XMLHttpRequest.responseText in XMLHttpRequest.onreadystatechange when XMLHttpRequest.readyState equals to XMLHttpRequest.DONE.

Here's an example (not compatible with IE6/7).

var xhr = new XMLHttpRequest();xhr.onreadystatechange = function() {    if (xhr.readyState == XMLHttpRequest.DONE) {        alert(xhr.responseText);    }}xhr.open('GET', 'http://example.com', true);xhr.send(null);

For better crossbrowser compatibility, not only with IE6/7, but also to cover some browser-specific memory leaks or bugs, and also for less verbosity with firing ajaxical requests, you could use jQuery.

$.get('http://example.com', function(responseText) {    alert(responseText);});

Note that you've to take the Same origin policy for JavaScript into account when not running at localhost. You may want to consider to create a proxy script at your domain.

I'd suggest looking into fetch. It is the ES5 equivalent and uses Promises. It is much more readable and easily customizable.

const url = "https://stackoverflow.com";fetch(url)    .then(        response => response.text() // .json(), etc.        // same as function(response) {return response.text();}    ).then(        html => console.log(html)    );