用js实现toLowerCase()、toUpperCase()？

Question

怎么像在C语言里面通过ASSIC码做转换？实现 string.prototype.toUpperCase()、string.prototype.toLowerCase()function UpperCase(s){    var str = s;    var arr = str.split("");    for(var i=0; i<arr.length; i++){         arr[i] = arr[i] + 'a' -'A';         }     str = arr.join("");    return str; }var s = "aaaSSF"; UpperCase(s); //NANNANNAN

Answer 1

function UpperCase(s) {

    var str = s;

    var arr = str.split("");

    var charCodeOfA = 'A'.charCodeAt();

    var charCodeOfZ = 'Z'.charCodeAt();

    var difference = charCodeOfA - 'a'.charCodeAt();

    var curChar;

    for(var i = 0; i < arr.length; i++) {

        curChar = arr[i].charCodeAt();

        arr[i] = (curChar < charCodeOfZ && curChar > charCodeOfA) ? arr[i] : String.fromCharCode(curChar + difference);    

    }

    

    str = arr.join("");

    return str;

}

var s = "aaaSSF";

UpperCase(s); //AAASSF