JSFiddle - React, Tailwind, and code Playground

HTML

<select name="dropdown[]">
  <option value="1">Sony</option>
  <option value="2">Nintendo</option>
  <option value="3">Microsoft</option>
</select>

<select name="dropdown[]">
  <option value="1">Sony</option>
  <option value="2">Nintendo</option>
  <option value="3">Microsoft</option>
</select>

<select name="dropdown[]">
  <option value="1">Sony</option>
  <option value="2">Nintendo</option>
  <option value="3">Microsoft</option>
</select>

JavaScript

$("select[name=dropdown\\[\\]]").change(function() {
    var value = this.value;
    
    $("select[name=dropdown\\[\\]]").not(this).val(value);
});