CSS: registerProperty() static method
The CSS.registerProperty()
static method registers
custom properties
, allowing for property type checking, default
values, and properties that do or do not inherit their value.
Registering a custom property allows you to tell the browser how the custom property should behave; what are allowed types, whether the custom property inherits its value, and what the default value of the custom property is.
Syntax
js
CSS.registerProperty(PropertyDefinition)
Parameters
A PropertyDefinition
dictionary object, which can contain the following
members:
name
-
A string representing the name of the property being defined.
syntax
Optional-
A string representing the expected syntax of the defined property. Defaults to
"*"
. inherits
-
A boolean value defining whether the defined property should be inherited (
true
), or not (false
). Defaults tofalse
. initialValue
Optional-
A string representing the initial value of the defined property.
Return value
undefined
.
Exceptions
InvalidModificationError
DOMException
-
The given
name
has already been registered. SyntaxError
DOMException
-
The given
name
isn't a valid custom property name (starts with two dashes, e.g.--foo
). TypeError
-
The required
name
and/orinherits
dictionary members were not provided.
Examples
The following will register a custom property
,
--my-color
, using registerProperty()
, as a color, give it a
default value, and have it not inherit its value:
js
window.CSS.registerProperty({
name: "--my-color",
syntax: "<color>",
inherits: false,
initialValue: "#c0ffee",
});
In this example, the custom property --my-color
has been registered using
the syntax <color>
. We can now use that property to transition a
gradient on hover or focus. Notice that with the registered property the transition
works, but that it doesn't with the unregistered property!
css
.registered {
--my-color: #c0ffee;
background-image: linear-gradient(to right, #fff, var(--my-color));
transition: --my-color 1s ease-in-out;
}
.registered:hover,
.registered:focus {
--my-color: #b4d455;
}
.unregistered {
--unregistered: #c0ffee;
background-image: linear-gradient(to right, #fff, var(--unregistered));
transition: --unregistered 1s ease-in-out;
}
.unregistered:hover,
.unregistered:focus {
--unregistered: #b4d455;
}
button {
font-size: 3vw;
}
We can add these styles to some buttons:
html
<button class="registered">Background Registered</button>
<button class="unregistered">Background Not Registered</button>
Specifications
Specification |
---|
CSS Properties and Values API Level 1 # the-registerproperty-function |
Browser compatibility
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