Question

我是JavaScript的初学者，我的代码遇到了麻烦。当它不输出答案时，我似乎无法弄清楚代码出了什么问题。我正在尝试将用户输入的罗马数字转换为其相应的印度阿拉伯数字。到目前为止，这是我的代码。

<!doctype html>
<html>
<body>
<h2>JavaScript Roman to Decimal Converter(1-10)</h2>
<p id="demo"></p>
<input id="roman" value=""/>
<button onclick="myFunction()">Convert</button>
</form>
<script>
function myFunction(){
    var sum=0;
        var len=romanNum.length();
        var i;

        var previous=10;
        for (i=0; i<len; i++)
        {
            switch (romanNum.charAt(i))
            {
            case 'X':
                sum=sum+10;
                if(previous<10)
                    sum=sum-2*previous;
                previous=10;
                break;

            case 'V':
                sum=sum+5;
                if(previous<5)
                    sum=sum-2*previous;
                previous=5;
                break;              

            case 'I':
                sum=sum+1;
                previous=1;

            }
        }
        decimalNum=sum;
    return decimalNum;

    document.getElementById("demo").innerHTML=decimalNum+" is the answer.";
</script>
</body>
</html>

Answer 1

here中最简单的解决方案，而不是复杂的switch语句。

var decimal = [1000, 500, 100, 50, 10, 5, 1];
var roman = ["M", "D", "C", "L", "X", "V", "I"];
  
function myFunction() {  

  var str = document.getElementById("roman").value;
  var result = 0;
  var decimal = [1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1];
  var roman = ["M", "CM","D","CD","C", "XC", "L", "XL", "X","IX","V","IV","I"];

  for (var i = 0;i<=decimal.length;i++) {

    while (str.indexOf(roman[i]) === 0){ //checking for the first characters in the string
    
      result += decimal[i];   //adding the decimal value to our result counter

      str = str.replace(roman[i],''); //remove the matched Roman letter from the beginning

    }
  }
  
  document.getElementById("demo").innerHTML = "<p style='color: green;'>The equivalent decimal for Roman Numeral " + str + " is " + result + "</p>";
  
}

<!doctype html>
<html>
<body>
<h2>JavaScript Roman to Decimal Converter(1-1000)</h2>
<p id="demo"></p>
<input id="roman" value=""/>
<button onclick="myFunction()">Convert</button>
</body>
</html>

Answer 2

在这里我创建了一个简短的演示，请检查我留下的评论https://jsbin.com/luceleqepe/edit?html,output

<!doctype html>
<html>
<body>
<h2>JavaScript Roman to Decimal Converter(1-10)</h2>
<p id="demo"></p>
<input id="roman" value=""/>
<button onclick="myFunction()">Convert</button>
</form>
<script>
function myFunction(){
  var sum=0;

  // you forgot to get romanNum value
  var romanNum = document.getElementById("roman").value;

  // String.length is an property not a method
  var len=romanNum.length;
  var i;

  var previous=10;
  for (i=0; i<len; i++)
  {
    switch (romanNum.charAt(i))
    {
      case 'X':
        sum=sum+10;
        if(previous<10)
          sum=sum-2*previous;
        previous=10;
        break;

      case 'V':
        sum=sum+5;
        if(previous<5)
          sum=sum-2*previous;
        previous=5;
        break;              

      case 'I':
        sum=sum+1;
        previous=1;

    }
  }
  decimalNum=sum;
  // no one experession will be executed, if it placed after return
  document.getElementById("demo").innerHTML=decimalNum+" is the answer.";
  return decimalNum;
  // also, you forgot to close the function
}
</script>
</body>
</html>

使用开关盒转换

2 个答案: