User:CamelCaseNick/statementCountsInCategories.js

Note: After publishing, you may have to bypass your browser's cache to see the changes.

Firefox / Safari: Hold Shift while clicking Reload, or press either Ctrl-F5 or Ctrl-R (⌘-R on a Mac)
Google Chrome: Press Ctrl-Shift-R (⌘-Shift-R on a Mac)
Internet Explorer / Edge: Hold Ctrl while clicking Refresh, or press Ctrl-F5
Opera: Press Ctrl-F5.

/**
 * Scripts that should achieve the same effect are
 * User:Lucas Werkmeister/addStatementCountsToCategories.js and User:Nikki/StatementCounts.js
 */
(async function() {
  if (mw.config.get("wgCanonicalNamespace") !== "Category") return;

  let links = [].slice.call(document.querySelectorAll("#mw-pages li a"))

  let query = `select ?article ?item ?statements where \{
  	             values ?article \{${links.map(link => link.href).map(iri => "<" + iri + ">").join("")}\}
  	             ?item ^schema:about ?article; wikibase:statements ?statements.
  	           \}`;
  let articlesStatementsMap = (await (await fetch("https://query.wikidata.org/sparql", {
    "method": "POST",
    headers: new Headers({
      "Accept": "application/sparql-results+json",
      "Content-Type": "application/x-www-form-urlencoded; charset=UTF-8"
    }),
    "body": "query=" + encodeURIComponent(query)
  })).json()).results.bindings;

  links.forEach(link => {
    let bindings = articlesStatementsMap.filter(t => t.article.value === link.href)
    if (bindings.length == 0) return;
    if (bindings.length > 1) throw new Error(`statement counts: ${link} was included multiple times`)
 
    const statements = bindings[0].statements.value
    const item = bindings[0].item.value

    let hint = document.createElement("a")
    hint.href = item
    hint.append(`${statements} st.`)

    hint.style.verticalAlign = "text-bottom"
    hint.style.marginLeft = "3px"
    hint.style.fontSize = ".8em"
    if (statements <= 5) hint.style.fontWeight = "bold"
    if (statements === 0) hint.style.color = "red"

    link.insertAdjacentElement("afterend", hint)
  });
}).call(window).catch(console.error);