CSSStyleDeclaration setProperty() Method

Set a new CSS property:

var declaration = document.styleSheets[0].cssRules[0].style;
var setprop = declaration.setProperty("background-color", "yellow");

Description

The setProperty() method sets a new or modifies an existing CSS property in a CSS declaration block.

Method
setProperty()	Yes	9.0	Yes	Yes	Yes

object.setProperty( propertyname, value, priority)

Parameter	Description
propertyname	Required. A String representing the name of the property to set
value	Required. A String representing the new value
priority	Optional. A String representing if the property's priority should be set to important or not. Legal values: "important" undefined ""

DOM Version:	CSS Object Model
Return Value:	undefined

Set a new CSS property with "important" priotrity:

var declaration = document.styleSheets[0].cssRules[0].style;
var setprop = declaration.setProperty("background-color", "yellow", "important");

Modify an existing CSS property:

var declaration = document.styleSheets[0].cssRules[0].style;
var setprop = declaration.setProperty("color", "blue");