Every client-side JavaScript application needs to communicate with the backend. In general, this communication is performed through an interface, which is exposed by the server-side application that relies on the HTTP protocol to transfer data through the JSON.
The traditional way of making a request to the server from AJAX applications (using XMLHttpRequests) involves getting a handle on the XMLHttpRequest object, making the request, reading the response, checking the error codes, and finally processing the server response. It goes something like this:
snippet
var xmlhttp = new XMLHttpRequest();
xmlhttp.onreadystatechange = function() {
if (xmlhttp.readystate == 4 && xmlhttp.status == 200) {
var response = xmlhttp.responseText;
} else if (xmlhttp.status == 400) { // or really anything in the 4 series
// Handle error gracefully
}
};
// Setup connection
xmlhttp.open(“GET”, “http: //myserver/api”, true);
// Make the request
xmlhttp.send();
