Imprimir una página web

Print a Web Page Using JavaScripthttp://www.htmlgoodies.com/beyond/javascript/article.php/3471121

By Joe Burns

with updates by HTMLGoodies Editorial Staff

You've probably been on a web page and wanted to print out the page for later reference. Wouldn't it be

great to be able to provide visitors to your site to be able to do just that? This tutorial for web developers

will show you how to use JavaScript's window.print function, complete with examples!

The JavaScript window.print() Function

Print is a method of the object "window." At first I thought that the command was simply capturing the

buttons along the top of the browser window so all I had to do was substitute "print" with one of the other

items, like "mail" or "home". No dice. I also tried setting up the same type of format with items found in the

menus like "properties" and "Options." Error after error. It's apparently put into the DTD as a method unto

itself.

Saving Grace!

The good thing about the command, the way the authors set it up, is that it does not immediately fire a

print. It actually only fires the print window, which still gives your site's visitors a choice in the matter!

It's then up to the person who triggered the method whether to then continue with the printing or not. That's

good because I can see a ton of problems with printers not being turned on and huge, huge files being set

to print.

So, how to you set up the code? Well, try this first and then look at the code:

Click to Print This Page

And here's the code:

<A HREF="javascript:window.print()">Click to Print This Page</A>

The JavaScript is triggered by using the command "javascript:" in place of a URL, thus allowing a

hypertext link to fire off the JavaScript.

And before you ask, yep, this will work with almost any JavaScript Event Handler as long as the format

allows you to write it as a specific line or trigger a function.

You can set it to print off of an image:

<A HREF="javascript:window.print()">

<IMG SRC="print_image.gif" BORDER="0"</A>

It looks like this as an image:

And yes, you can set it to trigger off a button:<FORM><INPUT TYPE="button" onClick="window.print()"></FORM>

It looks like this as a form button:To make sure that your visitors have JavaScript enabled before you provide them with a button that only works using JavaScript, you can use JavaScript to print out the button. That way if they have it disabled,

no button appears, saving them the frustration of clicking a button that does absolutely nothing:

<SCRIPT LANGUAGE="JavaScript">

if (window.print) {

document.write('<form><input type=button name=print value="Print"

onClick="window.print()"></form>');

}

</script>

Some Printing Suggestions

Okay, now you have the power to force a print request, but that doesn't mean to simply offer a print on any

page. You should make a point of being helpful to your users.

Make a Page for Printing - The Goodies tutorials, as you can see, have a wavy background, a

bunch of images, and stuff stuck in all over the place. They're not very good for printing. If I was

to offer this page for printing, I would make a point of creating basically a text-only page, or at

least a page with limited images and no background.

Make the Page Printer-Friendly - I would lose all text colors and make sure the widthof the page

was no more than 500px, left justified, so that what was shown on the screen would print on the

printed page in the same way.

Allow the User to Choose to Print - My print offering would be text at the bottom or an icon that

doesn't intrude. Everyone knows they can already print your pages without any help from your

coding. So, make this something you offer as a help rather than putting it into people's faces.

Never Attach This to a User Event - Don't set this to an onLoad, or an onMouseOver, or some

other user event. It will only tend to upset those who have visited your page and probably stop

them from coming back.

Additionally, there are more detailed methods of printing pages that allow you to separate the content from

the ads, site navigation, etc. This is easier if your content is separate from your site's design, i.e. in a

database. We'll go into those techniques in a later tutorial!

That's That...

There you go. Now you can set up a print request through JavaScript. If used correctly, this is a very nice

addition to a page and a help to the user, so use it wisely and well.

Enjoy!