How to Properly Encode Ampersands in JavaScript for HTML?

Encoding Ampersands in JavaScript

You encounter an issue where HTML encoding is lost when retrieving a value from a hidden input field. The value, encoded within the input field, appears in a textbox without proper encoding. This causes the '&' character to be interpreted literally, rather than as an HTML entity.

To resolve this issue, you can use JavaScript libraries or jQuery methods to encode the string.

DOMParser API

• Create a new DOMParser instance.
• Use the parseFromString method to parse an HTML string and create a new Document object.
• Retrieve the inner text of the created document, which will be HTML-encoded.

const parser = new DOMParser();
const encodedText = parser.parseFromString('<p>chalk &amp; cheese</p>', 'text/html').documentElement.textContent;

Custom JavaScript Functions

function htmlEncode(value) {
  // Create a temporary textarea element
  const textarea = document.createElement('textarea');
  textarea.textContent = value;
  const encodedValue = textarea.value;

  // Remove the created textarea element
  textarea.remove();

  return encodedValue;
}

Example Usage

const hiddenValue = $('#hiddenId').attr('value');
const encodedValue = htmlEncode(hiddenValue);
$('#textboxId').val(encodedValue);

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