CF7 input value

Get input field value from cf7 form

HTML

<label id="centi">Length (cm)
  <span class="wpcf7-form-control-wrap cm">
    <input type="number" name="cm" value="" class="wpcf7-form-control wpcf7-number wpcf7-validates-as-required">
  </span>
</label>
<br>
<label id="kilo"> weight (kg)
  <span class="wpcf7-form-control-wrap kilo">
    <input type="number" name="kilo" value="" class="wpcf7-form-control wpcf7-number wpcf7-validates-as-required wpcf7-validates-as-number">
  </span>
</label><br>
<a href="javascript:void(0);" id="getval">
  Get BMI
</a>
<br><span id="bmi"></span>

JavaScript

var button = document.getElementById("getval");
button.addEventListener("click", displayTextField);

function displayTextField() {
  var cm = document.getElementsByName("cm")[0].value * 1.0;
  var kilo = document.getElementsByName("kilo")[0].value * 1.0;
  var BMIvar = kilo / ((cm / 100) * (cm / 100));
  document.getElementById("bmi").textContent = "BMI is: " + BMIvar;
}