我在罗马数字转换函数中得到了一个意想不到的结果。它将正确计算1、2或4位数。它还可以正确地处理4位数的第3位。如果数字是3位,则计算百位和个位相同。
function convertToRoman(num) {
var evaluate = num.toString();
var replace = "";
var oneUnit;
var fiveUnit;
var tenUnit;
for (var i = 0; i < evaluate.length; i++ )
{
switch (evaluate.length | i)
{
case 1|0:
case 2|1:
case 3|2:
case 4|3:
oneUnit = "I";
fiveUnit = "V";
tenUnit = "X";
break;
case 2|0:
case 3|1:
case 4|2:
oneUnit = "X";
fiveUnit = "L";
tenUnit = "C";
break;
case 3|0:
case 4|1:
oneUnit = "C";
fiveUnit = "D";
tenUnit = "M";
break;
case 4|0:
oneUnit = "M";
fiveUnit = "MMMMM";
tenUnit = "MMMMMMMMMM";
break;
}
switch (evaluate.charAt(i))
{
case "1":
replace += oneUnit;
break;
case "2":
replace += oneUnit + oneUnit;
break;
case "3":
replace += oneUnit + oneUnit + oneUnit;
break;
case "4":
replace += oneUnit + fiveUnit;
break;
case "5":
replace += fiveUnit;
break;
case "6":
replace += fiveUnit + oneUnit;
break;
case "7":
replace += fiveUnit + oneUnit + oneUnit;
break;
case "8":
replace += fiveUnit + oneUnit + oneUnit + oneUnit;
break;
case "9":
replace += oneUnit + tenUnit;
break;
}
}
num = replace;
return num;
}
期望返回值为555:"DLV"返回555:"VVV"
期望返回值1555:"MDLV"Return for 1555: "MDLV"
为什么3位数字的前2位没有分配给正确的大小写?
您希望匹配一组值,但是switch语句只能根据其大小写值计算一个表达式。位或运算符在这里被误用了,因为结果不会是evaluate.length
和i
的值的连接。您应该将第一个switch块转换为一系列if/else语句。