How do I sandbox a particular element on a web page?

Question

I have this thing on my webpage... I guess it could be called a widget...

How do I separate it's CSS and JS from the containing page's CSS and JS? preferably without using an iframe?

In my app the user can customize the CSS of the content, so, I'd need a clean slate.

Answer 1

On the outermost element of your widget, set a relatively unique class name. For example:

<div class="my_spiffy_widget">
  <!-- Insert spiffy widget here -->
</div>

Put the Javascript and CSS in their own files. For the CSS, structure all of your selectors like this:

.my_spiffy_widget P { /* paragraph rules */ }
.my_spiffy_widget A { /* anchor rules */ }
.my_spiffy_widget UL { /* unordered list rules */ }

That ensures your rules do not accidentally get overridden by other CSS rules.

Likewise with the JavaScript, prefix your functions with a common, distinctive prefix:

function my_spiffy_widget_doSomething() {...}

Avoid global variables if possible, but if you cannot, prefix them as well:

var my_spiffy_widget_firstTime = true;

Answer 2

You could add the !important declaration in the properties, making it harder for the user to override the settings.

eg:

div.widget #header {
    padding-left: 10px !important;
    padding-right: 5px !important;
}

And/or you could grab a CSS reset script (such as Eric Meyer's) and preface each selector with the name of your container DIV.

Answer 3

You can give all elements outside very complex css class names and make sure they don't collide with the ones the user will choose (like "KAFHxyz_..."). This way, all sane class names and default styles will only apply to the "widget".

This will be some effort since you'll need to set all the standard CSS styles using !important (so the user can say "body { font ... }" and it will only apply to his area.

Alternatively, you could try to write some javascript which fetches all styles of all elements, then add the "widget" (and it's JS/CSS) and then reset all styles to what they were before. Should be possible but the performance will probably suck.

[EDIT] That said, you do know that you can create an iframe with JavaScript and manipulate the content (the DOM inside) to your hearts content, yes? In this scenario, the IFrame will just be a Div-like element which adds a "namespace" for CSS and JS files.