Question

使用Javascript切换单位转换语句。

Answer 1

You tried to use "unit" as js variable which is already part of loaded document, need to correct your code as below,

<!DOCTYPE html>
<html>
<body>

<p id="demo"></p>
<input id="units" type="number" placeholder="Feet" value="1"/>
<script>
var unit = document.getElementById("units").value;

switch (unit) {
    case 0:
        unit = valNum/3.2808;
        break;
    case 1:
        unit = valNum / 0.0022046;
        break;
document.getElementById("demo").innerHTML = "Today is " + unit;
</script>

</body>
</html>

Again, need to write separate function to load values from input field to screen. it could be event based like keypressed, mouse or simple button.

Answer 2

以下是您的代码中的一些问题：

未分配的变量valNum
输出在case 1:
switch-case中的语法错误。

function calc() {
  var unit = parseInt(document.getElementById("unit").value, 10) || -1;
  var feet = parseInt(document.getElementById("feet").value, 10) || 0;
  var result = 0;
  switch (unit) {
    case 0:
      result = 'Result is: ' + (feet / 3.2808);
      break;
    case 1:
      result = 'Result is: ' + (feet / 0.0022046);
      break;
    default:
      result = 'Unit ##.##';
      break;
  }
  document.getElementById("demo").innerHTML = result;
}

<p id="demo">Unit ##.##</p>
<input placeholder="Unit" oninput='calc()' id='unit' />
<input placeholder="Feet" oninput='calc()' id='feet' />

如何使用Javascript编写用于单位转换的Switch语句

2 个答案: