Function to only allow decimal input

isDecNumber.js

    if(typeof isDecNumber != 'function'){
        window.isDecNumber = function(e) {
            // backspace, tab, enter, end, home, left, right
            // we don't support the del key in Opera because del == . == 46.
            var controlKeys = [8, 9, 13, 35, 36, 37, 39, 46]
            // IE doesn't support indexOf
            var isControlKey = controlKeys.join(",").match(new RegExp(e.which))
            // some browsers just don't raise events for control keys. Easy.
            // e.g. Safari backspace.
            if (!e.which || // control keys in most browsers. e.g. Firefox tab is 0
                (48 <= e.which && e.which <= 57) ||                          // always 1 through 9
                (96 <= e.which && e.which <= 105) ||                         // always 1 through 9 (number block)
                (188 == e.which) || (190 == e.which) || (110 == e.which) ||  // allow comma and dot
                isControlKey) { // Opera assigns values for control keys.
                    // no leading 0
                    if( (48 == e.which || 96 == e.which) &&
                        (e.target.selectionStart < 1) )
                            e.preventDefault()
                    // only allow one comma and/or dot
                    if( (188 == e.which || 190 == e.which || 110 == e.which) &&
                        ( (e.target.value.indexOf(",") >= 0) ||
                          (e.target.value.indexOf(".") >= 0) )
                    )
                        e.preventDefault()
                    return true
            } else {
                e.preventDefault()
            }
        }
    }