cipher/index.html at master · Agboolafeyikemi/cipher · GitHub

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<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width" />

    <title>Cipher machine</title>

    <script>
      const alphabet = [
        "A",
        "B",
        "C",
        "D",
        "E",
        "F",
        "G",
        "H",
        "I",
        "J",
        "K",
        "L",
        "M",
        "N",
        "O",
        "P",
        "Q",
        "R",
        "S",
        "T",
        "U",
        "V",
        "W",
        "X",
        "Y",
        "Z",
      ];

      function encryptText() {
        const form = document.forms[0];

        let title = document.getElementById("titleId");

        title.innerHTML = "Encrypted text";

        let shift = Number(form.shift.value);

        let sourceText = form.sourceText.value;

        form.sourceText.value = [...sourceText]
          .map((char) => encrypt(char, shift))
          .join("");
      }

      function decryptText() {
        const form = document.forms[0];
        let title = document.getElementById("titleId");

        title.innerHTML = "Plain text";

        let shift = Number(form.shift.value);
        let sourceText = form.sourceText.value;

        shift = (alphabet.length - shift) % alphabet.length;

        form.sourceText.value = [...sourceText]
          .map((char) => encrypt(char, shift))
          .join("");
      }

      function encrypt(char, shift) {
        let include = alphabet.includes(char.toUpperCase());

        if (include) {
          let position = alphabet.indexOf(char.toUpperCase());

          let newPosition = (position + shift) % alphabet.length;
          return alphabet[newPosition];
        } else return char;
      }
    </script>
  </head>
  <body>
    <form>
      <h1>My Cipher machine</h1>
      <p id="titleId">Plain text</p>

      <div>
        <textarea
          name="sourceText"
          rows="8"
          cols="50"
          spellcheck="false"
          value=""
        >
        </textarea>
      </div>

      <div>
        <label for="shift">Shift:</label>
        <select id="shift" name="shift">
          <option value="1">1</option>
          <option value="2">2</option>
          <option value="5">5</option>
          <option value="10">10</option>
        </select>
      </div>

      <div>
        <input
          type="button"
          id="decrypt"
          value="Encrypt"
          onclick="encryptText();"
        />
        <input
          type="button"
          id="decrypt"
          value="Decrypt the text"
          onclick="decryptText();"
        />
      </div>
    </form>
  </body>
</html>