Returns [object HTMLSpanElement]

Question

<form>
   <table>
     <tr>
        <td>Distance:</td>
        <td><input type="number" id="distance" onKeyUp="calculate();">m</td>
     </tr>
     <tr>
        <td>Time:</td>
        <td><input type="number" id="time" onKeyUp="calculate();">s</td>
     </tr>
     <tr>
        <td>Speed:</td>
        <td><span id="speed">21</span><span id="unit">&nbsp;m/s</span></td>
     </tr>
  </table>
</form>

<script type="text/javascript">

   var calculate = function() {
      var distance = document.getElementById("distance").value;
      var time = document.getElementById("time").value;
      var speed = distance/time;}
      if (speed=="Infinity" || speed=="NaN") {
         document.getElementById("speed").innerHTML="Invalid Input";
         document.getElementById("unit").innerHTML="";
      } else {
         document.getElementById("speed").innerHTML=speed;
      }

</script>

I am making a simple speed calculator but it isn't working. The output comes [object HTMLSpanElement] Any help will be appreciated for I am new to javascript.

Answer 1

The variable speed in the last line is not the same as the one you set because it's in a different scope.

Try this:

var calculate = function() {
  var distance = document.getElementById("distance").value;
  var time = document.getElementById("time").value;
  var speed = distance/time;

  if (speed=="Infinity" || speed=="NaN"){
    document.getElementById("speed").innerHTML="Invalid Input";
    document.getElementById("unit").innerHTML="";
  }else{
    document.getElementById("speed").innerHTML=speed;
  }
};

Answer 2

The reason is scope:

var calculate = function() {
  var distance = document.getElementById("distance").value;
  var time = document.getElementById("time").value;
  var speed = distance/time;
}

// speed is not within the right scope anymore 
// because you closed the function above!
if (speed=="Infinity" || speed=="NaN"){
  document.getElementById("speed").innerHTML="Invalid Input";
  document.getElementById("unit").innerHTML="";
}else{
  document.getElementById("speed").innerHTML=speed;
}

Because your script runs in document, the value of speed is resolved as the element <span id="speed" ... >.

Move the last if-statement inside the function:

var calculate = function() {
  var distance = document.getElementById("distance").value;
  var time = document.getElementById("time").value;
  var speed = distance/time;

  if (speed=="Infinity" || speed=="NaN"){
    document.getElementById("speed").innerHTML="Invalid Input";
    document.getElementById("unit").innerHTML="";
  }else{
    document.getElementById("speed").innerHTML=speed;
  }
}