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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <title>-?\d+</title>
</head>
<body>
  <h1>Signed integers</h1>
  <pre id="out"></pre>
  <script>
    var values = ["42", "-7", "abc", "3.14"];
    document.getElementById("out").textContent = values.map(function (v) {
      return v + " → " + /^-?\d+$/.test(v);
    }).join("\n");
  </script>
</body>
</html>

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JavaScript RegExp ? quantifier — optional minus (Try It)