Archive for the ‘Javascript’ Category

How to detect if HTML document has fully initialized

Posted by: admin in Javascript on November 27th, 2011

Most programmers use the “onload” event to detect if the document has fully loaded, but there’s a flaws relying on this technique. The alternative of detecting is to check the DOM tree of the document.

For Firefox and Opera 9+, use “DOMContentLoaded‘

if ( document.addEventListener )

document.addEventListener(“DOMContentLoaded”, myFunction, false);

For Internet Explorer,

if  ( document.all && !window.opera ) { //

document.writer( ‘<script type=”text/javascript” id=”contentloadtag” defer=”defer” src=”javascript:void(0)”></script>’);

var contentloadtag = document.getElementById(“contentloadtag”);

contentloadtag.onreadystatechange = function() {

if ( this.readyState == “complete” ) [

myFunction();

}

}

}
Source

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‘null’ is null or not an object

Posted by: admin in Javascript on May 18th, 2010

This error occurs when the object/element you are trying to access does not exists in the html page or you did not specify the ID of the element.

or

You are executing a code while the html page has not yet fully loaded. If you need to execute a certain code during page load, this can be done on window.onload event or put the script before the end of the body tag .

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How to get Event object of Firefox

Posted by: admin in Javascript on April 9th, 2010

  1. function getEvent() {
  2.  if (window.event) return window.event;
  3.  else return getEvent.caller.arguments[0];
  4. }
  5.  
  6. function showMessage(){
  7. var e = getEvent();
  8.  
  9. // you can use this e object
  10. }

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How to refresh the page using javascript

Posted by: admin in DHML, Javascript on November 11th, 2009

3 Ways to refresh/reload the page using javascript

  1. <input type=”button” value=”Reload Page” onClick=”window.location.reload()”>
  2. <input type=”button” value=”Reload Page” onClick=”history.go(0)”>
  3. <input type=”button” value=”Reload Page” onClick=”window.location.href=window.location.href”>

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How to replace all occurrences in javascript

Posted by: admin in Javascript on October 10th, 2009

To replace all occurrences in a string use the “g” modifier without double quote like this

var strvar = “one two one”;

strvar = strvar.replace(/one/g,”1″);

the output of the strvar would be “1 two 1″

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Access denied in XmlHttpRequest

Posted by: admin in Ajax, Javascript on August 26th, 2009

It’s a security thing to prevent people from using AJAX between websites and servers.

Basically, whenever you write a URL in AJAX, it has to be the same URL as the website you are running the script on. Even the www. has to be the same.

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How to Load multiple function in javascript

Posted by: admin in Javascript on June 24th, 2009

  1. function AddLoadEvent(functionName) {
  2. var oldOnload = window.onload;
  3.  
  4. if (typeof window.onload != 'function') {
  5. window.onload = functionName;
  6. } else {
  7. window.onload = function() {
  8. oldOnload();
  9. functionName();
  10. }
  11. }
  12.  
  13. }


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How to Call more than one function on loading the web page

Posted by: admin in Javascript on May 18th, 2009

If you’re using the following method to invoke more than one function then you’re stuck, you will be wasting you time on debugging trying to figure out what’s the problem.

  1. function callMe1() {
  2. ….
  3. }
  4.  
  5. function callMe2() {
  6. ….
  7. }
  8.  
  9. window.onload = callMe1;
  10. window.onload = callMe2;

callMe2 function will replace callMe1 function, and only callMe2 function will run.

The workaround of this would be using the Anonymous Function

  1. window.onload = function() {
  2.              callMe1();
  3.              callMe2();
  4. }

Another way to overcome this kind of situation is to use the addLoadEvent function

  1. function addLoadEvent(func) {
  2.      var oldonload = window.onload;
  3.      if (typeof window.onload != 'function') {
  4.                window.onload = func;
  5.      } else {
  6.                window.onload = function() {
  7.                      oldonload();
  8.                      func();
  9.                }
  10.      }
  11. }
  12.  
  13. use this as follows
  14.  
  15. addLoadEvent(callMe1);
  16. addLoadEvent(callMe2);

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Calling function in Javascript

Posted by: admin in Javascript on May 18th, 2009

Creating a function in javascript is very simple but calling / invoking the function sometime gets tricky when a function don’t have a parameters, and wondering why the function is it not working….

Example:

  1. function countBodyChildren() {
  2.  var body_element = document.getElementsByTagName("body")[0];
  3.  
  4.  alert(body_element.childNodes.length);
  5. }

and you invoke the function like this

  1. window.onload = countBodyChildren();

when you run your program, nothing happens. So, what’s the problem?
In javascript, calling function without parameter should not have an open and close parenthesis, that’s all folk….:)

It should be

  1. window.onload = countBodyChildren;

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Javascript Functions

Posted by: admin in Javascript on March 30th, 2009

Function Literal Notation:

var f = function(){ return 1; }

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