javascript - 为什么我的密码总是只正确加密第一个字母而不是第二个、第三个字母等

Question

所以我一直在制作这个密码，现在如果我输入'a'并移动1，它会输出'b'，这是正确的，但如果我输入'ab'或任何其他长度的字符串它例如，输出为“bl”。我该如何解决这个问题？

function encryption(str, amount) {
  var str = document.getElementById('inputText').value;
  var amount = document.getElementById('amountDropdown').value;
  var result = "";
  //loop through each character in word
  for (var i = 0; i < str.length; i++) {
    var c = str.charCodeAt(i);
    //If the character is uppercase
    if ((c >= 65) && (c <= 90)) {
      result += String.fromCharCode(((c - 65 + amount) % 26) + 65);
    }
    //if the character is lowercase
    else if ((c >= 97) && (c <= 122)) {
      result += String.fromCharCode(((c - 97 + amount) % 26) + 97);
    }
    //if the character isn't a letter
    else {
      result += str.charAt(i);
    }
  }
  //return the result
  outputResult.innerHTML = "The text you have input has been encrypted to.." + result;
}

function decryption() {
  var str = document.getElementById('inputText').value;
  var amount = document.getElementById('amountDropdown').value;
  var result = "";
  //loop through each character in word
  for (var i = 0; i < str.length; i++) {
    var c = str.charCodeAt(i);
    //If the character is uppercase
    if (c >= 65 && c <= 90) {
      result += String.fromCharCode((c - 65 - amount) % 26 + 65);
    }
    //if the character is lowercase
    else if (c >= 97 && c <= 122) {
      result += String.fromCharCode((c - 97 - amount) % 26 + 97);
    }
    //if the character isn't a letter
    else {
      result += str.charAt(i);
    }
  }
  //return the result
  outputResult.innerHTML = "The text you have input has been encrypted to.." + result;
}

function encryptClickHandler() {
  document.getElementById('inputText').value = encrypt(document.getElementById('inputText').value, document.getElementById('amount').value);
}

function decryptClickHandler() {
  document.getElementById('inputText').value = decrypt(document.getElementById('inputText').value, document.getElementById('amount').value);
}

Answer 1

输入字段的值始终是字符串。

当您计算(c - 97 - amount) % 26时，您会得到以下结果:

c = 97, amount = 1    => (97 - 97 + 1)   % 26 = (0 + 1)   % 26 = 1    % 26 = 1
c = 98, amount = 1    => (98 - 97 + 1)   % 26 = (1 + 1)   % 26 = 2    % 26 = 2
c = 97, amount = '1'  => (97 - 97 + '1') % 26 = (0 + '1') % 26 = '01' % 26 = 1
c = 98, amount = '1'  => (98 - 97 + '1') % 26 = (1 + '1') % 26 = '11' % 26 = 11

要解决此问题，请将值转换为整数:

var amount = parseInt(document.getElementById('amountDropdown').value, 10);