This example gets the CSSPageDescriptors for a @page at-rule, if the object is supported on the browser, and then logs its properties.
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 @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 document stylesheet at index 1, 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.styleSheets[1].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.
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HTML:
3.2
| Encoding:
UTF-8
| Version:
0.7.4