XMLHttpRequest does nothing....?

Question

I am new to javascript and AJAX, and have spent the last 8 hours on this one problem, and its beating me. I know its simple, just can't find what I am doing wrong. I have an image on my site with a with an on-click=SendCommand() . This is the js code that I have

function SendCommand(){
        alert("BingoBango!");

        var xmlhttp = new XMLHttpRequest();
        xmlhttp.open("GET","https://www.justanexample.com/API/MobileAPP/SendCommand.php?apikey=7785adf3a5d3a3adsf555nb5v55bsaer5v&mac=b827eb6ffa19&command=2",true);
        xmlhttp.send();
};

I get the alert message, and I get no errors using firebug or in chrome javascript console. However that page is not executed. I can however copy and paste that exact url into the browser and it executes successfully.

Any help would be GREATLY appreciated, its kickin my butt.

What do you expect to happen? What do you see in the network tab? — SLaks, Feb 05 '14 at 20:39
Are you seeing a new request appear in the browser dev tools/network tab? If not, the request isn't being sent. — helion3, Feb 05 '14 at 20:40
Let me check that, thanks for the quick responses!! Also, just had a thought, the ssl cert on the server is self signed, could that cause a problem? — chuckycharms, Feb 05 '14 at 20:43
It does show that it has loaded OK. Size of the content is listed "From Cache".....Cause of the problem? — chuckycharms, Feb 05 '14 at 20:44
What makes you think it didn't execute? Something you expect to see on the server, or something you expect to see in the browser? — Jason P, Feb 05 '14 at 20:45
The page it is calling is calling a python script as well as updating a mysql record. This works fine and I can see the results when called directly from a browser — chuckycharms, Feb 05 '14 at 20:45
Sorry, that wasnt very clear. I am expecting to see the python script run on my device, as well as see the mysql table get updated, It is not. I dont expect to see anything in the browser. — chuckycharms, Feb 05 '14 at 20:47
If the browser returns a cached response, it didn't actually make the request to the server. — Jason P, Feb 05 '14 at 20:47
is there something i can do in my request to ask it to not use the browser cache and actually hit my server? — chuckycharms, Feb 05 '14 at 20:48
What I generally do is to get the current time in milliseconds and append that as a url parameter. — Jason P, Feb 05 '14 at 20:51

score 1 · Accepted Answer · edited May 23 '17 at 12:03

1

The page it is calling is calling a python script as well as updating a mysql record. Is there something i can do in my request to ask it to not use the browser cache and actually hit my server?

You should not use a GET request for things that execute actions on the server. Use POST instead, which should not be cached.

If that doesn't help, adapt your HTTP cache headers or, as a last resort, append random strings to the url.

edited May 23 '17 at 12:03

Community

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answered Feb 05 '14 at 20:52

Bergi

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And you should not post comments in the answers section ;) – Niet the Dark Absol Feb 05 '14 at 20:56
@Niet: It's short, but it's an answer, isn't it? – Bergi Feb 05 '14 at 20:57
Well, now it is XD The problem is caused by cache headers. – Niet the Dark Absol Feb 05 '14 at 20:58
Thanks to JasonP!! My issue was that the request was getting a cached response. Adding a random number to the url worked. For example the new url is xmlhttp.open("GET","https://www.justanexample.com/API/MobileAPP/SendCommand.php?apikey=7785adf3a5d3a3adsf555nb5v55bsaer5v&mac=b827eb6ffa19&command=2&r=" + Math.random(),true); – chuckycharms Feb 05 '14 at 20:59
I am confused right now about the concept of "response cache", first encounter, as far as I understood right now the SERVER does not react on same domain request, if...? And how does the server identify that? @Jasonp – loveNoHate Feb 05 '14 at 21:27

score 0 · Answer 2 · answered Feb 05 '14 at 20:50

This is how I would do it

JS

function SendCommand()
{
var xmlhttp;
if (window.XMLHttpRequest)
  {// code for IE7+, Firefox, Chrome, Opera, Safari
  xmlhttp=new XMLHttpRequest();
  }
else
  {// code for IE6, IE5
  xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
  }
xmlhttp.onreadystatechange=function()
  {
  if (xmlhttp.readyState==4 && xmlhttp.status==200)
    {
    document.getElementById("myDiv").innerHTML=xmlhttp.responseText;
    }
}
xmlhttp.open("GET","https://www.justanexample.com/API/MobileAPP/SendCommand.php?apikey=7785adf3a5d3a3adsf555nb5v55bsaer5v&mac=b827eb6ffa19&command=2",true);
xmlhttp.send();
}

HTML

<button type="button" onclick="SendCommand()">My button</button>
<div id="myDiv"></div>

XMLHttpRequest does nothing....?

2 Answers2