Chrome的覆盖范围标签是什么意思？

Chrome浏览器的Coverage标签提供了网站代码测试工具的功能。它可以生成一个网站的代码覆盖分析报告，显示哪些代码已经被执行并标记未被执行的代码。这个分析报告可以帮助开发人员发现无用代码，提高网站性能。

下面是一些使用Chrome的Coverage标签的示例代码：

1. 检查home.html页面覆盖范围，并输出未覆盖的部分

fetch('home.html')
  .then(response => response.text())
  .then(html => {
    const parser = new DOMParser();
    const doc = parser.parseFromString(html, 'text/html');
    const jsFiles = doc.querySelectorAll('script[src]');
    const fileUrls = [...jsFiles].map(jsFile => jsFile.getAttribute('src'));

    Promise.all(fileUrls.map(fetch))
      .then(responses => Promise.all(responses.map(response => response.text())))
      .then(scripts => {
        const uncovered = [];
        const coverage = window.__coverage__ || {};
        scripts.forEach((script, i) => {
          const url = fileUrls[i];
          const instrumentation = new Function(`
            const __coverage__ = {};
            ${script}
            return __coverage__;
          `);
          const scriptCoverage = instrumentation();
          const uncoveredRanges = findUncoveredRanges(scriptCoverage);
          uncoveredRanges.forEach(range => {
            range.forEach(entry => {
              uncovered.push({ url, range: entry });
            });
          });

          Object.assign(coverage, scriptCoverage);
        });

        console.log(`Uncovered ranges in ${location}:\n\n${JSON.stringify(uncovered, null, 2)}`);
        window.__coverage__ = coverage;
      })
      .catch(console.error);
  })
  .catch(console.error);

function findUncoveredRanges(coverage) {
  return Object.keys(coverage).map(filename => {
    const ranges = [];
    let start = null;
    coverage[filename].forEach((count, i) => {
      if (!start && !count) {
        start = i;
      } else if (start && count) {
        ranges.push([start, i - 1]);
        start = null;
      }
    });
    if (start !== null) {
      ranges.push([start, coverage[filename].length - 1]);
    }
    return ranges;
  }).reduce((a, b) => a.concat(b), []);
}

2. 将页面与活动XSS Payload检查的覆盖范围合并

const PAGE_LOADED_EVENT = new Event('page