Detect which prefixed css calc to use via javascript

prefixedCalc.js

// public domain, use it for whatever
// returns "calc", "-moz-calc", etc
// (no -ms because they already support it non-prefixed)

function prefixedCalc () {
    var prefixes = ["","-webkit-","-moz-","-o-"], el
    for (var i = 0; i < prefixes.length; i++) {
        el = document.createElement('div')
        el.style.cssText = "width:" + prefixes[i] + "calc(9px)"
        if (el.style.length) return prefixes[i] + "calc"
    }
}