This could be a bit more efficient. You can either do a single for p in primary_widgets and then append to two lists, or you could use itertools like this:

# This at the top:
from itertools import groupby

...

# and then here:
grouped = groupby(
    primary_widgets,
    lambda p: primary_widget_selections[p.widget_id] == '1')
selected_primary_widgets = grouped[True]
unselected_primary_widgets = grouped[False]

Same here about iterating over the list twice.

If several widgets don't have given positions, won't this result in several of the values in positions being set to the same thing (len(widgets))? Is that a problem?
If not, I'd like to see that reflected in your testing, and some comment about how it's handled added here.

Can you just use .rb-icon-delete for your elements? I don't like having duplicate names for icons.

It might be worth assigning the selector (or selector string) to a variable to reduce the length of this line.

Please wrap this string in gettext(...)

This will run the selector three times. You should chain this as such:

$('#' + widgetID)
    .removeClass('widget-masonry-item')
    .parent()
        .masonry('reload')
        .end()
    .hide();

No spaces inside of the parens.

No spaces inside of the parens.

It looks like this code will result in four HTTP requests (and possibly two confirm() dialogs)? Can we maybe rewire things to get that down to one?

Careful about trailing whitespace.

It's old code, but this could be simplified to use {{widget.collapsed|yesno:"expand,collapse"}} instead of the if/else.

This hsould be marked for translation.

Mark for translation.

How did you come up with this number?

How did you come up with this number?

I'm not pleased about all the magic numbers in here. Some of them (like the .btn) could probably use right-alignment instead of left to make it more sensible. Other (like the image widths) would be nice to define in a variable.

Add a space between the # and the comment.

Can you combine these two into one rule?

#all-primary-widgets, #all-secondary-widgets {
  display: none;
}

Can you combine these into one rule?

Could just use a // single-line comment.

This should use ===

Instead of spelling out "index" and "element", it's just as clear and quicker to read to use "i" and "el"

These two lines should be combined (} else {)

Can you combine these into a single var statement?

var selectionData = ...,
    widgetCheckbox = ...;

If you combine the first two lines into one, you'd save some indentation (and even if you don't, there's some misalignment in the indentation of the last few lines).

This line needs a semicolon.

Add a space between the // and the comment.

Add a space between the // and the comment.

This should use ===

You call $(element) twice. It would be nice to assign that to a variable so you only have to run the jquery selector once.

It looks like you're calling append() and passing in a selector? I'm not sure what this does.

This should use ===

"Save Widgets" should be localized. Probably you'll need to do that beforehand, like this:

function createWidgetAdderModals() {
    var buttonText = gettext("Save Widgets"),
        buttons = {};

    buttons[buttonText] = function() {
        ...
    };
    $('#large-widget-modal').dialog({
        ...
        buttons: buttons,
        ...
    });

    buttons[buttonText] = function() {
        ...
    };
    ...

Can you wrap this comment to be as close to 80 columns on the first line as you can?

Space between the // and the comment.

All variables should be declared at the beginning of the function, even if you wait until here to assign them (due to how javascript does hoisting). If you run jshint on your code it should tell you about that.

Space between the // and the comment.

Should use ===.

Combine these together (} else {)

Template tags like this should all be left-aligned, and should operate on a sort of separate indentation "namespace" than the HTML. See reviewboard/templates/reviews/review_request_box.html for a good example. Please fix up all of this throughout this template (which wasn't completely correct to begin with).

Ship It!