files/en-us/web/api/csspagedescriptors/index.md
{{APIRef("CSSOM")}}
The CSSPageDescriptors interface represents a CSS declaration block for an {{cssxref("@page")}} at-rule.
The interface exposes style information and various style-related methods and properties for the page.
Each multi-word property has versions in camel- and snake-case.
This means, for example, that you can access the margin-top CSS property using the syntax style["margin-top"] or style.marginTop (where style is a CSSPageDescriptor).
A CSSPageDescriptors object is accessed through the {{DOMxRef("CSSPageRule.style", "style")}} property of the CSSPageRule interface, which can in turn be found using the {{DOMxRef("CSSStyleSheet")}} API.
{{InheritanceDiagram}}
This interface also inherits properties of its parent, {{domxref("CSSStyleDeclaration")}}.
The following property names, in kebab-case (accessed using bracket notation) and camel-case (accessed using dot notation), each represent the value of a descriptor in the corresponding @page at-rule:
margin
margin property of the corresponding @page at-rule.margin-top or marginTop
margin-top property of the corresponding @page at-rule.margin-right or marginRight
margin-right property of the corresponding @page at-rule.margin-bottom or marginBottom
margin-bottom property of the corresponding @page at-rule.margin-left or marginLeft
margin-left property of the corresponding @page at-rule.page-orientation or pageOrientation {{experimental_inline}}
page-orientation property of the corresponding @page at-rule.size
size property of the corresponding @page at-rule.This interface inherits the methods of its parent, {{domxref("CSSStyleDeclaration")}}.
This example gets the CSSPageDescriptors for a {{cssxref("@page")}} at-rule, if the object is supported on the browser, and then logs its properties.
<pre id="log"></pre>
const logElement = document.querySelector("#log");
function log(text) {
logElement.innerText = `${logElement.innerText}${text}\n`;
logElement.scrollTop = logElement.scrollHeight;
}
#log {
height: 280px;
overflow: scroll;
padding: 0.5rem;
border: 1px solid black;
}
Below we define styles for the page using a {{cssxref("@page")}} at-rule.
We assign different values for each margin property using the margin shorthand, and also specify the size.
We don't set the page-orientation.
This allows us to see how the properties map in the Web API object.
@page {
margin: 1cm 2px 3px 4px;
/* page-orientation: upright; */
size: A4;
}
First we check if CSSPageDescriptors is defined on the global window object, and if not we log that the interface is not supported.
If CSSPageDescriptors is supported, we get the target stylesheet, and then gets the cssRules defined in that stylesheet.
We need to get this stylesheet because the example is embedded in a separate frame with its own sheet (index 0 is the CSS for this page).
We then iterate through the rules defined for the live example and match any that are of type CSSPageRule, as these correspond to @page rules.
For the matching objects we then log the style and all its values.
if (typeof window.CSSPageDescriptors === "undefined") {
log("CSSPageDescriptors is not supported on this browser.");
} else {
// Get stylesheets for example and then get its cssRules
const myRules = document.getElementById("css-output").sheet.cssRules;
for (const rule of myRules) {
if (rule instanceof CSSPageRule) {
log(`${rule.style}`);
log(`margin: ${rule.style.margin}`);
// Access properties using CamelCase syntax
log(`marginTop: ${rule.style.marginTop}`);
log(`marginRight: ${rule.style.marginRight}`);
log(`marginBottom: ${rule.style.marginBottom}`);
log(`marginLeft: ${rule.style.marginLeft}`);
log(`pageOrientation: ${rule.style.pageOrientation}`);
// Access properties using snake-case syntax
log(`margin-top: ${rule.style["margin-top"]}`);
log(`margin-right: ${rule.style["margin-right"]}`);
log(`margin-left: ${rule.style["margin-left"]}`);
log(`margin-bottom: ${rule.style["margin-bottom"]}`);
log(`page-orientation: ${rule.style["page-orientation"]}`);
log(`size: ${rule.style.size}`);
// Log the original CSS text using inherited property: cssText
log(`cssText: ${rule.style.cssText}`);
log("\n");
}
}
}
The results are shown below.
Note that the style object displayed at the top of the log should be a CSSPageDescriptors to match the current specification, but may be a CSSStyleDeclaration in some browsers.
Note also that the corresponding values for properties in camel- and snake-case match each other and the @page declaration, and that page-orientation is the empty string "" because it is not defined in @page.
{{EmbedLiveSample("Inspecting a page at-rule", "100%", "350px")}}
{{Specifications}}
{{Compat}}