Use javascript to determine if an ASP.NET page is a postback

Question

Hi, Is it possible to determine if an ASP.NET page is a postback from javascript? So basically a javascript equivalent of C# Page.IsPostBack.

Thanks.

Answer 1

I would just put a render tag in the javascript

var isPostBack = <%= Page.IsPostback ? "true" : "false" %>;

Putting the "true" and "false" as strings should be done to eliminate any possible issues converting the type to a string as in C# true.ToString() is usually "True" which is an error in javascript.

Answer 2

Sure. Just use your server code to write out a javascript flag, if you really need this.

But I suspect you're barking up the wrong tree here.

Answer 3

I'm not exactly sure of what you are trying to do but you might want to look into the PageRequestManagerClass:

http://www.asp.net/AJAX/Documentation/Live/ClientReference/Sys.WebForms/PageRequestManagerClass/default.aspx

It exposes events for all different parts of the request.

Answer 4

Just a minor detail here, C# (and JavaScript) are case-sensitive languages so the accepted answer above will not work.

It should be:

var isPostBack = <%= Page.IsPostBack ? "true" : "false" %>; 

vs.

var isPostBack = <%= Page.IsPostback ? "true" : "false" %>; 

Pre-emptive snarky comment: Please use the comment feature for corrections to answers like this.

(I would have commented had I enough rep to do so but haven't)