My practice is to build the DOM programmatically with jQuery, and add styles to the elements directly

   $("<div>")
     .css({width: 100, height: 20, color: 'red'})
     .appendTo(container);

Then, since these are just values in normal javascript code, you can refactor as normal. Pull commonly used patterns out into functions (e.g. `importantText(16, "size 16 important text goes here")`).

Most styles in the applications I write tend to be inextricably linked to the layout and function of a component (e.g., tabs should be next to each other); in the rare case that a style needs to be customized in different locations or at different times, it becomes a parameter (e.g. `confirmDialog(textStyle, message, onOk, onCancel)`)

No extra tools are needed, beyond jQuery (building up the DOM without jQuery or something like it is awful).

I've made this argument before, using JS exclusively for styling does not let you avoid CSS. It lets you avoid certain aspects of CSS that may, or may not, be helpful.