javascript - 如何测试一个字符是数字、大写还是小写？

Question

我试图让这段 JavaScript 运行。我不断收到一条错误消息：

ThisChar.toUpperCase() is not a function 

我曾尝试使用 jsfiddle.net，但似乎无法解决此错误。这是怎么回事？

// CREATE ARRAY OF CHARACTERS
CharacterArray = ["1", "2", "3", "a", "b", "c", "D", "E", "F", "/", "+", ")"];

// TEST CHARACTERS 
function testCharacters() {
   // GET ARRAY LEN
   var CharacterArrayLen = CharacterArray.length;
   // LOOP THROUGH ARRAY
   for (i = 0; i < CharacterArrayLen; i++) {
       // PARSE SINGLE CHARACTER
       var ThisChar = CharacterArray.slice(i, i + 1);
       if (!isNaN(ThisChar * 1)) {
           alert(ThisChar + ' is numeric!');
       } else {
           if (ThisChar == ThisChar.toUpperCase()) {
               alert(ThisChar + ' is upper case true');
           } else if (ThisChar == ThisChar.toLowerCase()) {
               alert(ThisChar + " is lower case");
           } else {
               alert(ThisChar + " is unknown");
           }
       }
   }
}
testCharacters();​

Answer 1

.slice总是返回一个数组。只需访问元素：

var ThisChar = CharacterArray[i];

---

您不必将值乘以*1，传递给的值isNaN将隐式转换为数字：

!isNaN(ThisChar)