JS script for checking broken links (also include unavailable anchors on the same page)

check-broken-links.js

// Script for checking broken links (also include unavailable anchors on the same page)

// Note:
// Due to cross-domain issues, we can't count the numbers of the errors for cross-domain URL.
// So we can only count the broken links that are in the same domain.
// For those cross-domain links, please check the error messages in the console.

async function doCheck() {
  // The HTML block id to find links
  var id = 'content';

  var ele = document.getElementById(id).getElementsByTagName('a');
  var x = 0;
  var error_links = {};
  for (var i = 0; i < ele.length; i++) {
    var href = ele[i].getAttribute('href');
    if (href) {
      await fetch(href, {
        method: 'HEAD',
        mode: 'no-cors',
      }).then((response) => {
        // For cross-domain links, we can't check the status code, so we have to pass them.
        // However, we can check the error messages in the console if there're issues.
        if (response.ok || response.type == 'opaque') {
          ele[i].style.border = '2px dotted green';
          // Check anchors on the same page.
          if (href.startsWith('#')) {
            if (document.querySelectorAll(href).length !== 1) {
              x++;
              error_links[href] = "There're " + document.querySelectorAll(href).length + " elements matching";
              ele[i].style.border = '2px dotted red';
            }
          }
        } else {
          x++;
          error_links[href] = response.status + ": " + response.statusText;
          ele[i].style.border = '2px dotted red';
        }
      }).catch((error) => {
        x++;
        error_links[href] = error.message;
        ele[i].style.border = '2px dotted red';
      });
    }
  }
  console.log(error_links);
  console.log("Done, " + x + " broken links found.");
  return error_links;
}

doCheck();