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Asked: 2026-05-22T01:45:38+00:00

I’m trying to get more familiar with HTML5. I am an experienced programmer, but

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I’m trying to get more familiar with HTML5. I am an experienced programmer, but a javascript neophyte. I’ve written some code to getCurrentPosition (which results in an async callback when the position is fixed). Here’s the code (I already tested for, and got a positive response on, support for geolocation on this platform):

 function tryGeo() {
     document.write("asking for location <br>");
     try {
       navigator.geolocation.getCurrentPosition(savePos);
   } catch (e) {
     document.write("Excpn in asking for location <br>");
   }
     document.write("have asked for location <br>");
}

When that code runs, it pops up the permission request window or dialog. I grant permission. This is on Firefox 3.6.8 on MacOS 10.6.7.

Some time later, the callback to savePos() happens (when the position is known):

function savePos(pos) {
   lat = pos.coords.latitude;
   lon = pos.coords.longitude;
   document.write("have got location lat " +lat+ ", lon " +lon+ " <br>");
}

The problem I’m having is that that document.write() moves to a new blank page. Instead, I want to add the text to the page I was rendering when I make the getCurrentPosition() request. How can I do that?

I’m probably making some trivial beginner’s error – please let me know what.

Also, links to “learn javascript for Experienced Coders” resources would be appreciated. Thaks,

Peter

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1 Answer

  1. Editorial Team

    That’s just how document.write works:

    Writing to a document that has already loaded without calling document.open() will automatically perform a document.open call.

    And document.open:

    If a document exists in the target, this method clears it.

    And their example just above that note:

    // In this example, the document contents are 
// overwritten as the document 
// is reinitialized on open(). 
document.write("<html><p>remove me</p></html>"); 
document.open(); 
// document is empty.

    The easiest thing to do is to have an element already on the page and then update that element’s content. So, you’d have a bit of HTML:

    <p id="you-are-here"></p>

    And then in the callback:

    document.getElementById('you-are-here').innerHTML = "have got location lat " + lat + ", lon " + lon;

    So, yeah, your trivial beginner’s error is using document.write on a document that has already loaded.

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