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JavaScript AJAX Basics (retiring) Programming AJAX Introducing JSON

Rob McClara
Rob McClara
19,257 Points

A web server 'response' is returned in the form of text. How do we know what format the web server is using?

I understand the concepts of structured data formats like JSON and XML. However, I'm confused on how you know what format, if any, the web server will return.

Let's say I am wanting a response formatted in JSON from the web server. If the 'response' is in another format, it will not work.

2 Answers

Jonathan Grieve
Jonathan Grieve
Treehouse Moderator 90,705 Points

You don't need to worry about this really. There's a very simple method of sorting out how the server handles the request which is called "Parsing".

What this does is converts the information into a format that will work for you.

var employees = JSON.parse(xhr.responseText);

In this example, the method is stored in a variable. and the responseText (the information sent back) is converted from plainText to something AJAX friendly. So all the legwork is done for you.

Hope this helps. :)

1,781 Points

When a server writes its response they can fill in options such as Content-Type which can be a lot of different things like

res.writeHead(200, {"Content-Type": "text/javascript"});


res.writeHead(200, {"Content-Type": "text/plain"});


res.writeHead(200, {"Content-Type": "application/json"});