This feature is experimental. It may be changed or removed in a future version without prior notice or deprecation.
Receives a computed CSS property value for the given element, casted as a number.
The value is casted by removing the property's unit (which is usually
px for computed properties).
The result is then parsed as a floating point number.
undefined if the property value is missing, or if it cannot
be parsed as a number.
When requesting a single CSS property, its value will be returned as a string:
value = up.element.style(element, 'font-size') // value is '16px' value = up.element.styleNumber(element, 'font-size') // value is 16
A single property name in kebab-case or camelCase.