Question

Is there any way to achieve a += operator within the css operator (assuming ui.value in the example has a numerical value)

Something like this(which doesn’t work):

$("#resume_holder").contents().find('body').children().css('font-size', +=ui.value);

Answer 1

Try:

$("#resume_holder")
    .contents()
    .find('body')
    .children()
    .css('font-size', '+=' + ui.value);

(if you’re using jQuery >= 1.6)

according to the docs for css:

As of jQuery 1.6, .css() accepts relative values similar to
.animate(). Relative values are a string starting with += or -= to
increment or decrement the current value. For example, if an element’s
padding-left was 10px, .css( “padding-left”, “+=15” ) would result in
a total padding-left of 25px.

Example: http://jsfiddle.net/JMRPf/ (trivial I know, but proof that it works)