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  <title>Lodash _.mapKeys - basic transform</title>
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  <h1>_.mapKeys - uppercase &amp; prefix keys</h1>
  <pre id="out"></pre>
  <script src="https://cdn.jsdelivr.net/npm/lodash@4.17.21/lodash.min.js"></script>
  <script>
    (function () {
      var counts = { a: 1, b: 2, c: 3 };
      var upper = _.mapKeys(counts, function (value, key) {
        return key.toUpperCase();
      });
      var prefixed = _.mapKeys(counts, function (value, key) {
        return "n_" + key;
      });
      var lines = [
        "upper    : " + JSON.stringify(upper),
        "prefixed : " + JSON.stringify(prefixed),
        "source   : " + JSON.stringify(counts)
      ];
      document.getElementById("out").textContent = lines.join("\n");
    })();
  </script>
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Lodash _.mapKeys - uppercase and prefix keys (Try It)