StylePropertyMap: append() method

The append() method of the StylePropertyMap interface adds one or more values to the end of a list-valued CSS property's value list.

A list-valued CSS property is one whose value is a comma-separated list of terms, such as background-image or animation.

Syntax

append(property)
append(property, value1)
append(property, value1, value2)
append(property, value1, value2, /* …, */ valueN)

Parameters

property

An identifier indicating the stylistic feature (e.g., font, width, background color) to add.

value1, …, valueN

One or more values to add to the end of property's value list, in the order given.

Return value

None (undefined).

Exceptions

TypeError

Thrown if:

• property is not a valid CSS list-valued property.
• Any of value1, …, valueN is already associated with a different property (for example, a value read from one property's entry in a StylePropertyMap, then passed to append() for another property).
• Any of value1, …, valueN is a CSSUnparsedValue or CSSVariableReferenceValue object.
• property's current value contains a var() reference.

Examples

Basic usage

This example shows an extra background image value being added to the background-image property of the element, using HTMLElement.attributeStyleMap.

// get the button element
const buttonEl = document.querySelector("button");

// append another value to the background-image property set on the attribute
buttonEl.attributeStyleMap.append(
  "background-image",
  "linear-gradient(180deg, blue, black)",
);

Specifications

• CSS Typed OM Level 1