what's the logic of ajax
function loadDoc() {
//step 1. as you clearly understand
var xhttp = new XMLHttpRequest();
//step 2. Here you are defining the function that should run once the data is 'ready'
xhttp.onreadystatechange = function() {
if (this.readyState == 4 && this.status == 200) {
document.getElementById("demo").innerHTML = this.responseText;
}
};
//step 3. Define what type of request you are making (param 1) and where you are making that request to (param 2)
//you are also setting a boolean if the request should be asynchronous (param 3) . Note: that should always be true
xhttp.open("GET", "ajax_info.txt", true);
//step 4. Send the request to the server resource you defined in step 3.
xhttp.send();
}