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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Slow regexp</title>
</head>
<body>
  <script>
    function convertHtmlToText(html) {
      el.innerHTML = html;

      return el.textContent || el.innerText;
    }

    var el = document.createElement('div'),
      a = convertHtmlToText('a'),
      b = convertHtmlToText('b'),
      space = convertHtmlToText(' '),
      nonBreakingSpace = convertHtmlToText('&nbsp;'),
      slowRegExpTrim = /^(\s|\u00A0)+|(\s|\u00A0)+$/g,
      spaces,
      text;

    alert('Open console');
    console.log(slowRegExpTrim);
    setTimeout(function() {
      for(var tests = 0; tests < 32; tests++) {
        spaces = '';
        for(var i = tests; i; i--) spaces += space + nonBreakingSpace;

        text = a + spaces + b;

        console.log(tests, text);

        console.time('Slow regexp');
        text.replace(slowRegExpTrim, '');
        console.timeEnd('Slow regexp');
      }
    }, 5000);
  </script>
</body>
</html>