Coverage class

The Coverage class provides methods to gather information about parts of JavaScript and CSS that were used by the page.

Signature

export declare class Coverage

Remarks

To output coverage in a form consumable by Istanbul, see puppeteer-to-istanbul.

The constructor for this class is marked as internal. Third-party code should not call the constructor directly or create subclasses that extend the Coverage class.

Example

An example of using JavaScript and CSS coverage to get percentage of initially executed code:

// Enable both JavaScript and CSS coverage
await Promise.all([
  page.coverage.startJSCoverage(),
  page.coverage.startCSSCoverage(),
]);
// Navigate to page
await page.goto('https://example.com');
// Disable both JavaScript and CSS coverage
const [jsCoverage, cssCoverage] = await Promise.all([
  page.coverage.stopJSCoverage(),
  page.coverage.stopCSSCoverage(),
]);
let totalBytes = 0;
let usedBytes = 0;
const coverage = [...jsCoverage, ...cssCoverage];
for (const entry of coverage) {
  totalBytes += entry.text.length;
  for (const range of entry.ranges) usedBytes += range.end - range.start - 1;
}
console.log(`Bytes used: ${(usedBytes / totalBytes) * 100}%`);

Methods

Method	Modifiers	Description
startCSSCoverage(options)
startJSCoverage(options)		Remarks: Anonymous scripts are ones that don't have an associated url. These are scripts that are dynamically created on the page using eval or new Function. If reportAnonymousScripts is set to true, anonymous scripts URL will start with debugger://VM (unless a magic //# sourceURL comment is present, in which case that will the be URL).
stopCSSCoverage()		Promise that resolves to the array of coverage reports for all stylesheets. Remarks: CSS Coverage doesn't include dynamically injected style tags without sourceURLs.
stopJSCoverage()		Promise that resolves to the array of coverage reports for all scripts. Remarks: JavaScript Coverage doesn't include anonymous scripts by default. However, scripts with sourceURLs are reported.