How to change the value of checkbox when i select a value from select input using js

window.addEventListener("load", function() { // on page load
  document.getElementById("myselectbox1").addEventListener("change", function() {
    document.getElementById("mycheckbox1").value = this.value;
  });
  document.getElementById("mycheckbox1").addEventListener("change", function() {
    console.log(this.value);
  });
});

<input type="checkbox" name="id" value="" id="mycheckbox1">

<select name="cat-1" id="myselectbox1">
  <option value="">Choose</option>
  <option value="100">Value1</option>
  <option value="200">Value2</option>
</select>