## jQuery.cssNumber Returns: Object

Description: 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.

- #### version added: 1.4.3jQuery.cssNumber

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.

1 |
    jQuery.cssNumber.someCSSProp = true;

By default the object contains the following properties:

- `zIndex`
- `fontWeight`
- `opacity`
- `zoom`
- `lineHeight`
- `widows` (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)