window onload not invoking when the page gets loaded [closed]

Not seeing al alert of “let’s go!”

<html>

<head>
  <script type="text/javascript">
    function simple() {
      alert("let's go!");
    }
    window.onload = simple;
    async function getPlatforms() {
      alert "hello"
      const response = await fetch(
        'http://10.64.127.94:5000/api/get_platforms', {
          method: 'GET',
        }
      );
      const data = await response.json();
      alert data
    }

    function selects() {
      var ele = document.getElementsByName('chk');
      for (var i = 0; i < ele.length; i++) {
        if (ele[i].type == 'checkbox')
          ele[i].checked = true;
      }
    }

    function deSelect() {
      var ele = document.getElementsByName('chk');
      for (var i = 0; i < ele.length; i++) {
        if (ele[i].type == 'checkbox')
          ele[i].checked = false;
      }
    }
    <!--        function SubmitForm(formId) {-->
    <!--            var oForm = document.getElementById(formId);-->
    <!--            if (oForm) {-->
    <!--                oForm.submit();-->
    <!--            }-->
    <!--            else {-->
    <!--                alert("DEBUG - could not find element " + formId);-->
    <!--            }-->
    <!--        }-->
  </script>
  <style>
    table,
    th,
    td {
      border: 1px solid black;
      border-collapse: collapse;
    }
  </style>
  <title>Unified Performance Heat Map</title>
</head>

<body>
  <h1 style="text-align: center;">Unified Performance Heat Map</h1>
  <hr>
  <form name="device_form" id="device_form">
    <label>Choose a device:</label>
    <select name="device_select" id="device_select">
    </select>
  </form>
  <br>
  <br>
  <label>Select the label:</label>
  <select name="label_select" id="label_select">
  </select>
  <br>
  <br>
  <label>Select the baseline:</label>
  <select name="label_baseline" id="label_baseline">
  </select>
  <br>
  <br>
  <label>Select the features:</label>
  <br>

  <br>
  <input type="button" onclick='selects()' value="Select All" />
  <input type="button" onclick='deSelect()' value="Deselect All" />

  <br>
  <br>
  <button type="button">Make Heat Map !</button>
  <hr>
  <table style="width:100%">
    <tr>
      <td>FEATURE</td>
      <td colspan="3" style="text-align: center;">IPSEC</td>
    </tr>
    <tr>
      <td>PACKET</td>
      <td>64</td>
      <td>IMIX</td>
      <td>1400</td>
    </tr>
    <tr>
      <td>BASE</td>
      <td>&nbsp;</td>
      <td>&nbsp;</td>
      <td>&nbsp;</td>
    </tr>
    <tr>
      <td>LABEL</td>
      <td>&nbsp;</td>
      <td>&nbsp;</td>
      <td>&nbsp;</td>
    </tr>
    <tr>
      <td>HEATMAP</td>
      <td>&nbsp;</td>
      <td>&nbsp;</td>
      <td>&nbsp;</td>
    </tr>
  </table>
</body>

</html>