JSFiddle - React, Tailwind, and code Playground

HTML

<div class="form-group">
            <label class="control-label col-md-2">From</label>
            <div class="col-md-3">
              <div class="input-group">
                <span class="input-group-addon">$</span><input class="form-control" name="FromL" placeholder="0" type="text" disabled></input>
              </div>
            </div>
            <label class="control-label col-md-1">To</label>
            <div class="col-md-3">
              <div class="input-group">
                <span class="input-group-addon">$</span><input class="form-control" name="ToL" placeholder="eg. 60,000" id="firstFieldId" type="text"></input>
              </div>
            </div>
      </div>
      
      <div class="form-group">
            <label class="control-label col-md-2">Rate</label>
            <div class="col-md-3">
              <div class="input-group">
                <input class="form-control" name="RateL" placeholder="eg. 16" type="text"><span class="input-group-addon">%</span></input>
              </div>
            </div>
      </div>
      
      <br><br>
      
       <div class="form-group">
            <label class="control-label col-md-2">From</label>
            <div class="col-md-3">
              <div class="input-group">
                <span class="input-group-addon">$</span><input class="form-control" name="FromM" placeholder="eg. 60,000" type="text" id="secondFieldId" disabled></input>
              </div>
            </div>
            <label class="control-label col-md-1">To</label>
            <div class="col-md-3">
              <div class="input-group">
                <span class="input-group-addon">$</span><input class="form-control" name="ToM" placeholder="eg. 100,000" type="text" id="thirdFieldId"></input>
              </div>
            </div>
      </div>
          
      <div class="form-group">
            <label class="control-label col-md-2">Rate</label>
            <div class="col-md-3">
              <div...

JavaScript

window.onload = function () {
  var first = document.getElementById('firstFieldId'),
      second = document.getElementById('secondFieldId'),
	  third = document.getElementById('thirdFieldId'),
      fourth = document.getElementById('fourthFieldId');

  first.onchange = function () {
    second.value = first.value;
  third.onchange = function () {
	fourth.value = third.value;
};
};
};