How do I make this conversion function work in both directions?

Question

I'm new in JS and I have trouble to finish a converter only with inputs, I explain the problem ! We have two input, Meters and Feet. when I transmit a number to Feet I have the result in Meters. And I Want to do the same think with Meters . and vice versa

let metresEl = document.getElementById('inputMetres');


function LengthConverter(valNum) {
    metresEl.value = valNum/3.2808;
}

  <div class="container">
    <div class="form-group">
      <label>Feet</label>
      <input type="number" id="inputFeet" placeholder="Feet" oninput="LengthConverter(this.value)" onchange="LengthConverter(this.value)" >
    </div>
    <div class="form-group">
      <label>Metres</label>
      <input type="number" id="inputMetres" placeholder="Metres">
    </div>
  </div>

Answer 1

You can add another parameter in the LengthConvertor function which will say the input unit (meter or feet) and convert it accordingly inside the function using if.

function LengthConverter(valNum, inputUnit) {
   if(inputUnit === 'feet')
    metresEl.value = valNum/3.2808;
   if(inputUnit === 'meter')
    feetsEL.value = valNum * 3.2808;
}


<div class="container">
    <div class="form-group">
      <label>Feet</label>
      <input type="number" id="inputFeet" placeholder="Feet" oninput="LengthConverter(this.value,"feet")" onchange="LengthConverter(this.value,"feet")" >
    </div>
    <div class="form-group">
      <label>Metres</label>
      <input type="number" id="inputMetres" placeholder="Metres" oninput="LengthConverter(this.value,"meter")" onchange="LengthConverter(this.value,"meter")" >
    </div>
  </div>