jQuery.cssNumber
An object containing all CSS properties that may be used without a unit. The .css() method uses this object to see if it may append px to unitless values.
jQuery.cssNumber()🡢 Object
You can think about jQuery.cssNumber as a list of all CSS properties you might use without a unit. It's used by .css() to determine if it needs to add px to unitless values.
The keys of the jQuery.cssNumber object are camel-cased and the values are all set to true. If you want to prevent the .css() method from automatically adding the px unit for a specific CSS property, you can add an extra property to the jQuery.cssNumber object.
jQuery.cssNumber.someCSSProp = true;
By default the object contains the following properties:
zIndexfontWeightopacityzoomlineHeightwidows(added in jQuery 1.6)orphans(added in jQuery 1.6)fillOpacity(added in jQuery 1.6.2)columnCount(added in jQuery 1.9)order(added in jQuery 1.10.2)flexGrow(added in jQuery 1.11.1)flexShrink(added in jQuery 1.11.1)