Wednesday 3 August 2011

JavaScript: the good old window.open (with a trick)

   


The window.open JavaScript method is one of most used in web sites. To be honest, it has been a little bit overused in the past and today lightbox effects are preferred. However I still use it, especially when displaying a large image.
In this article I will show you how to open a new window and resize it appropriately.

The opening
First of all, we have to decide which element will open a new window. Imagine we want to open a new window when the user clicks on an image. The window will contain a larger image. Our small picture will be something like:
<a href="javascript:void(popupImg('images/gallery/big/01.jpg'))"><img src="images/gallery/small/01.jpg" alt=""></a>
When the user clicks on the image, the popupImg function will be called.
If you prefer, we can use the onClick event:
<img src="images/gallery/small/01.jpg" alt="" onClick="popupImg('images/gallery/big/01.jpg')">

The function
The open() method has a simple syntax. We are talking about a method applied to the window object:
window.open (URL, windowName[, windowFeatures])
where: 
URL is the URL of the page to be opened;
windowName  is the name or target of the new window. It can be:
    _blank  -  a new window;
    _parent  -  the URL is loaded in the parent window;
    _self  -  the URL replaces the window;
    _top  -  the URL replaces the frame set;
    name - the name of the window;
windowFeatures  are features assigned to the new window. Those features can be:
    status  -  can be yes, no, 0 or 1 (default is yes) - display the status bar;
    titlebar  -  can be yes, no, 0 or 1 (default is yes) - display the title bar;
    toolbar  -  can be yes, no, 0 or 1 (default is yes) - display the tool bar;
    menubar  -  can be yes, no, 0 or 1 (default is yes) - display the menu bar;
    height  -  in pixels - determine the height;
    width  -   in pixels - determine the width;
    top  -   in pixels - determine the top position;
    left  -  in pixels - determine the left position;
    location  -  can be yes, no, 0 or 1 (default is yes) - display the address bar;
    fullscreen  -  can be yes, no, 0 or 1 (default is no) - display in full screen or not;
    channelmode  -  can be yes, no, 0 or 1 (default is no and for IE only) - display in theater mode or not;
    directories  -  can be yes, no, 0 or 1 (default is yes and for IE only) - display directories button or not.

We are going to use some of those optional features.

The popupImg function
Let's see the function:
function popupImg(url)
    {
The function has a parameter: the url we passed when the function is called ("images/gallery/big/01.jpg" in our example). That's where we get the content of the new window.
    prev = window.open("","_blank","resizable=no,scrollbars=no,location=no,menubar=no,status=no,toolbar=no");
    prev.document.open();
We open the new window using the open() method and pass just a few optional parameters. What we basically do is open a new blank window, with "_blank". This will make open a new and empty window.
    prev.document.writeln("<html><head><title>Preview</title></head>")
    prev.document.writeln("<body bottommargin=0 leftmargin=0 marginheight=0 marginwidth=0 rightmargin=0 topmargin=0>");
Then we start writing inside the new window inserting the <head> and <title>. We open the <body> tag and give it a few parameters.
    prev.document.writeln("<script type='text/javascript'>");
    prev.document.writeln("function completeImg() {");
    prev.document.writeln("i = document.getElementById(\"imm\");");
    prev.document.writeln("window.resizeTo(i.width + 6, i.height + 80);");
    prev.document.writeln("window.moveTo((screen.width - i.width) / 2, (screen.height - i.height) / 2);");
    prev.document.writeln("}");
    prev.document.writeln("</script>");
The previous part is inserting a JavaScript script, with a function called completeImg. The function will resize the window and move it to the center of the screen, once the image is completely loaded.
    prev.document.writeln("<a href=\"javascript:window.close();\">");
    prev.document.writeln("<img src=\""+url+"\" hspace=\"0\" vspace=\"0\" border=\"0\" alt=\"\" id=\"imm\" name=\"imm\" onload=\"return completeImg();\">");
    prev.document.writeln("</a>");
The previous part is inserting the image surrounded by an <a> tag so that when the user click the image, the new window will close. Then there's the completeImg function called when the image is loaded (onLoad).
    prev.document.writeln("</body>");
    prev.document.writeln("</html>");
    prev.document.close();
}
Finally we close everything.

The example shown should be considered as an exercise. I actually use it sometimes and it works very well. You should check the part which resizes and centers the new window, because you may need to adjust it a bit, considering the size of your image.

Hope you find it useful.

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