onclick go full screen

I realize this is a very old question, and that the answers provided were adequate, since is active and I came across this by doing some research on fullscreen, I leave here one update to this topic:

There is a way to "simulate" the F11 key, but cannot be automated, the user actually needs to click a button for example, in order to trigger the full screen mode.

• Toggle Fullscreen status on button click

  With this example, the user can switch to and from fullscreen mode by clicking a button:

  HTML element to act as trigger:

  <input type="button" value="click to toggle fullscreen" onclick="toggleFullScreen()">
  

  JavaScript:

  function toggleFullScreen() {
    if ((document.fullScreenElement && document.fullScreenElement !== null) ||    
     (!document.mozFullScreen && !document.webkitIsFullScreen)) {
      if (document.documentElement.requestFullScreen) {  
        document.documentElement.requestFullScreen();  
      } else if (document.documentElement.mozRequestFullScreen) {  
        document.documentElement.mozRequestFullScreen();  
      } else if (document.documentElement.webkitRequestFullScreen) {  
        document.documentElement.webkitRequestFullScreen(Element.ALLOW_KEYBOARD_INPUT);  
      }  
    } else {  
      if (document.cancelFullScreen) {  
        document.cancelFullScreen();  
      } else if (document.mozCancelFullScreen) {  
        document.mozCancelFullScreen();  
      } else if (document.webkitCancelFullScreen) {  
        document.webkitCancelFullScreen();  
      }  
    }  
  }
  

• Go to Fullscreen on button click

  This example allows you to enable full screen mode without making alternation, ie you switch to full screen but to return to the normal screen will have to use the F11 key:

  HTML element to act as trigger:

  <input type="button" value="click to go fullscreen" onclick="requestFullScreen()">
  

  JavaScript:

  function requestFullScreen() {
  
    var el = document.body;
  
    // Supports most browsers and their versions.
    var requestMethod = el.requestFullScreen || el.webkitRequestFullScreen 
    || el.mozRequestFullScreen || el.msRequestFullScreen;
  
    if (requestMethod) {
  
      // Native full screen.
      requestMethod.call(el);
  
    } else if (typeof window.ActiveXObject !== "undefined") {
  
      // Older IE.
      var wscript = new ActiveXObject("WScript.Shell");
  
      if (wscript !== null) {
        wscript.SendKeys("{F11}");
      }
    }
  }
  

Sources found along with useful information on this subject:

Mozilla Developer Network

How to make in Javascript full screen windows (stretching all over the screen)

How to make browser full screen using F11 key event through JavaScript

Chrome Fullscreen API

jQuery fullscreen event plugin, version 0.2.0

jquery-fullscreen-plugin

It's possible with JavaScript.

var elem = document.getElementById("myvideo");
if (elem.requestFullscreen) {
  elem.requestFullscreen();
} else if (elem.msRequestFullscreen) {
  elem.msRequestFullscreen();
} else if (elem.mozRequestFullScreen) {
  elem.mozRequestFullScreen();
} else if (elem.webkitRequestFullscreen) {
  elem.webkitRequestFullscreen();
}

Short personal bookmarklet version

javascript: document.body.webkitRequestFullScreen(); 

go fullscreen ← You can drag this link to your bookmark bar to create the bookmarklet, but you have to edit its URL afterwards: Delete everything before javascript, including the single slash: http://delete_me/javascript:[…]

This works for me in Google Chrome. You have to test whether it works in your environment and otherwise use a different wording of the function call, e.g. javascript:document.body.requestFullScreen(); – see the other answers for the possible variants.

_{Based on the answers by @Zuul and @default – thanks!}

If you want to switch the whole tab to fullscreen (just like F11 keypress) document.documentElement is the element you are looking for:

function go_full_screen(){
    var elem = document.documentElement;
    if (elem.requestFullscreen) {
      elem.requestFullscreen();
    } else if (elem.msRequestFullscreen) {
      elem.msRequestFullscreen();
    } else if (elem.mozRequestFullScreen) {
      elem.mozRequestFullScreen();
    } else if (elem.webkitRequestFullscreen) {
      elem.webkitRequestFullscreen();
    }
}