Javascript Code I cannot understand

Question

1.00/5 (1 vote)

See more:

Hi
I am having trouble looking for the error in my program and I have this code but I do not understand it. Can someone explain it to me. Thanks in advance.

JavaScript

function addItem(str) {
	  if (str=="") {
		document.getElementById("txtHint").innerHTML="";
		return;
	  } 
	  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("txtHint").innerHTML=xmlhttp.responseText;
		}
	  }
	  xmlhttp.open("GET","checkinout-actions/add-more-items-code.php?q="+str,true);
	  xmlhttp.send();
	  window.location.reload();
	}

Posted 22-Apr-15 16:48pm

Michelle Anne E. Rigor

Add a Solution

Comments

Sergey Alexandrovich Kryukov 22-Apr-15 23:09pm

Explaining code makes no sense at all, unless you ask some specific questions. We don't know your level, so, in general, it could be equivalent to teaching you whole JavaScript and programming, which hardly would be practical. Specific questions, please.
—SA

3 solutions

Solution 2

This link at the site Peter Leow listed might help you.

http://www.w3schools.com/php/php_ajax_php.asp[^]

Posted 22-Apr-15 17:10pm

Bill_Hallahan

Updated 22-Apr-15 17:14pm

v2

Solution 3

Please see my comment to the question.

Just in case, two hints:

The call window.XMLHttpRequest means AJAX: http://en.wikipedia.org/wiki/Ajax_(programming)[^].

And the call xmlhttp = new ActiveXObject("Microsoft.XMLHTTP") means one of the biggest abuse one can possibly do using JavaScript, as well as assuming that somebody would use IE5 or IE6. Even Microsoft advised to completely deny serving any Web content to such users, probably purely hypothetical. Using ActiveXObject is utterly unsafe, too, and "real" browser won't support it.

—SA

Posted 22-Apr-15 17:14pm

Sergey Alexandrovich Kryukov

Updated 22-Apr-15 17:15pm

v2

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Peter Leow · Accepted Answer · 2015-04-22T17:09:00

The is a javascript function that takes an argument called "str".
This code will clear the value of an html element called "txtHint" and return if the argument is empty:

C#

if (str=="") {
  document.getElementById("txtHint").innerHTML="";
  return;
}

Otherwise, the second part of the code is passing this argument as query string to a server-side script called "add-more-items-code.php" using Ajax method. The response from this server-side script will be displayed in "txtHint". You can learn about Ajax by going through this tutorial:
http://www.w3schools.com/ajax/default.asp[^]
The last line of code reload your browser, this will also clear the value in the "txtHint". If that is not what you want, then comment it out like this:

//window.location.reload();