JavaScript Browser Detection

Detecting your viewer's browser

Browser detection allows you to find out what browser your viewer is using, and then perform a script based on it-- or just to send a friendly message to those with your favorite browser.

There are two objects often used for this, the navigator.appName and navigator.appVersion objects. The first one returns the name of the browser, the second returns the version of the browser.
If the browser is Netscape, navigator.appName returns the string "Netscape". If it is Internet Explorer, it returns the string "Microsoft Internet Explorer". Using just this, you could make a script to alert people as to what browser they are using (just to bug them). Like this:

You can do the same thing with the navigator.appVersion, except you will most likely want to grab just the integer from the version information (2,3,4, etc.). To do this, we use the parseInt() function:

var browserVer=parseInt(navigator.appVersion); 

Now, it returns only the integer value and not something like version 4.51. It just sends back 4 in that case. Thus, we could alert viewers as to whether their browser is new enough for us or not:

you can use both objects to be more exact. You could look for a certain set of browsers and only if they are above a certain version:

JavaScript Password Protection

Adding a password to your page

Password Protected Page
this script in the HEAD section of the page you want to protect. In this case, it was "jex8.htm". Here is the script:

---

---

If you have been through the previous tutorials, most of the code will make sense to you. Let's get to the details of what is going on with this thing:
var password;
This creates a variable named "password".
var pass1="cool";
This creates a password that will be accepted by the script. We name it pass1 in case we would like to have more than one acceptable password. ( ie pass2, pass3 etc. ).
password=prompt('Please enter your password to view this page!',' ');
This is what creates the prompt for the user to enter a password. Whatever the user enters in the prompt will be the value of the variable "password". If you have not seen prompts before, go to the prompts tutorial for more info.
if (password==pass1)
alert('Password Correct! Click OK to enter!');
This is where we verify the password. The variable "password" is what the user just typed into the prompt. The variable "pass1" is the only password we will accept. If they are the same, we send them an alert that the password was OK and they can continue. If you haven't seen if/else statements yet, go to the if/else page. For more on alerts, see the alerts page.
else
{
window.location="http://www.pageresource.com/jscript/jpass.htm";
}
This is what happens when they type in an incorrect password. We send them to a page of our choice. In IE4, it looks like nothing happened, it just reloads this page. In NS3 and 4 you will probably see the protected page for a quarter of a second. I said it wasn't the most secure script out there, so I would recommend the links at the end of the tutorial so you can get a more secure script. I chose to send it back to this page (jpass.htm), but you can type any url here you want. Maybe you could use something like:
window.location="http://www.barbie.com";
Make them cringe a little.......
All that's left after that is to link to the protected page from another page, like my link above to the example. No problem.
Now, if you want more than one acceptable password, you can make a couple of modifications and you will have it.
First, add more variables for the accepted passwords. If you want three good passwords, declare three variables. Since I had one named "pass1" already, I will just use "pass2" and "pass3":

var pass1="cool";

var pass2="awesome";

var pass3="geekazoid";

Next, you will need to change your "if" statement to include the other two passwords. This is done with the || (or) operator:

if (password==pass1 || password==pass2 || password==pass3)

  alert('Password Correct! Click OK to enter!');

This means that if the user typed in the correct value for "pass1" OR "pass2" OR "pass3", the password is correct and they can view the page.
Here is how the full code would look for this:

var password;

var pass1="cool";

var pass2="awesome";

var pass3="geekazoid";

password=prompt('Please enter your password to view this page!',' ');

if (password==pass1 || password==pass2 || password==pass3)

  alert('Password Correct! Click OK to enter!');

else

   {

    window.location="http://www.pageresource.com/jscript/jpass.htm";

    }

Foward and Back Buttons

How to make JavaScript history buttons

Well, you want to make a back button- but you want the button to take the viewer back to the page they just came from, which may not have been one of your pages. This kind of back button would act like the back button on a web browser. Well, if you really want to have one, you can do it with a nifty little javascript. Here it is:

This will place a button on your page that will send the user back to the last page in their history list before yours. To try it out, click the link below and see the button on the new page.
Example Page
And when you clicked the button, you ended up back here. You can try going to the example page from elsewhere......you'll just be sent back there when you click the button....

So, what does all of that code mean? Okay, here's the scoop:

1.

This opens a form so we can use the button on the page.

2.
This creates the button we use for the script.

3. ....onClick="history.back()">
This is what makes everything happen. The onClick=" " tells the browser to do the command in the quotes when the button is clicked. The history.back() is the function that does just what it says: It takes the viewer on step back in their history list.
Is there more? ..I thought you'd never ask......
Okay, you can swap out the history.back() function above with one of the following to do some different things:

1. history.forward()
This will take the viewer one step forward in their history list.

2. history.go(-1) or history.go(1)
This allows you to determine how far forward or back to take the viewer. Use a minus sign and a number to go back, or just a number to go forward.