javascript - 返回 [对象 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>

我正在制作一个简单的速度计算器，但它不工作。输出来自 [object HTMLSpanElement]我是 javascript 的新手，我们将不胜感激。

Answer 1

最后一行的变量speed与你设置的不一样，因为它在不同的范围内。

试试这个:

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;
  }
};