# Đoạn mã JavaScript để thêm ký tự đặc biệt vào đầu mỗi dòng trong văn bản nhiều dòng (ok)

### Bản nâng cấp&#x20;

```html
<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    .login-form {
      width: 300px;
      margin: 0 auto;
      padding: 20px;
      border: 1px solid #ccc;
      border-radius: 5px;
      background-color: #f2f2f2;
      text-align: center;
    }
    .form-group {
      margin-bottom: 15px;
    }
    .form-group textarea {
      width: 100%;
      padding: 10px;
      border: 1px solid #ccc;
      border-radius: 3px;
    }
    label {
      display: block;
      margin-bottom: 5px;
    }
    input {
      width: 100%;
      padding: 10px;
      border: 1px solid #ccc;
      border-radius: 3px;
    }
    button {
      background-color: #4CAF50;
      color: white;
      padding: 10px 20px;
      border: none;
      border-radius: 3px;
      cursor: pointer;
    }
  </style>
</head>
<body>
  <div style=" width: 800px; margin: 0 auto; ">
    <div class="form-group">
      <label for="specialChar">specialChar:</label>
      <input type="text" id="specialChar" name="specialChar">
    </div>
    <div class="form-group">
      <label for="originalText">originalText:</label>
      <textarea id="originalText" name="note" rows="10"></textarea>
    </div>
    <pre id="result"></pre>
    <button id="getmodifiedText" type="submit" style=" user-select: none; ">Submit</button>
  </div>
  <script>
    function addSpecialCharToLines(text, specialChar) {
      // Split the text into an array of lines
      const lines = text.split('\n');
      // Add the special character to the beginning of each line
      var modifiedLines = lines.map(line => specialChar + " " + line.trim());
      modifiedLines = modifiedLines.filter(function (el) {
        return el != specialChar + " ";
      });
      console.log(modifiedLines);
      // Join the modified lines back into a single string
      var modifiedText = modifiedLines.join('\n');
      console.log(modifiedText);
      return modifiedText;
    }
    document.getElementById("originalText").addEventListener("input", function () {
      var originalText = document.getElementById("originalText").value;
      var result = document.getElementById("result");
      var specialChar = document.getElementById("specialChar").value;
      if (specialChar == "") {
        specialChar = "▪️";
      }
      const modifiedText = addSpecialCharToLines(originalText, specialChar);
      result.innerText =  modifiedText;
    });
  </script>
</body>
</html>
```

<figure><img src="https://2494213435-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-LYjAG13rAPdbArSfRyB%2Fuploads%2FD3tOxFKDFKmDCcQUyPI1%2Fimage.png?alt=media&#x26;token=30b2610d-4888-42a8-bbda-d4385472b59e" alt=""><figcaption></figcaption></figure>

Bản gốc

```html
<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <script>
    function addSpecialCharToLines(text, specialChar) {
      // Split the text into an array of lines
      const lines = text.split('\n');
      // Add the special character to the beginning of each line
      const modifiedLines = lines.map(line => specialChar + " " + line.trim());
      modifiedLines.shift();
      modifiedLines.pop();
      // Join the modified lines back into a single string
      const modifiedText = modifiedLines.join('\n');
      return modifiedText;
    }
    // Example usage:
    const originalText = `
    This is the first line.
    This is the second line.
    This is the third line.
    `;
    const specialChar = '▪️';
    const modifiedText = addSpecialCharToLines(originalText, specialChar);
    console.log(modifiedText);
  </script>
</body>
</html>
```

<figure><img src="https://2494213435-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-LYjAG13rAPdbArSfRyB%2Fuploads%2FseSXEPQf0lcVpNAQaBXV%2Fimage.png?alt=media&#x26;token=eeb3c062-0089-4071-bbe5-2175e924b9bb" alt=""><figcaption></figcaption></figure>
