How Do I Get the Character-Based Caret Position in a Textarea?

Obtaining Character-Based Caret Position in Textarea

Determining the caret position in a textarea element can be a challenge, especially when seeking the exact column index in characters. Here's a breakdown of how you can achieve this:

For Firefox and Safari

Gecko-based browsers like Firefox and Safari seamlessly provide the selectionStart property on textareas. This property represents the position of the caret in characters from the beginning of the element.

For Internet Explorer

Unfortunately, Internet Explorer does not offer straightforward access to the caret position. Instead, you'll need to resort to a more intricate approach:

• Create Selection Range: Use createRange() to generate a selection range object.
• Duplicate Selection: Create a duplicate of the selection range for comparison purposes.
• Move Selection Boundary: Modify the duplicate selection to include a newline character at the beginning of the element text.
• Compare Selection Length: Subtract the length of the duplicate selection from the original selection length to determine the position of the caret.

Complete Code Example

The following JavaScript code demonstrates how to retrieve the caret position in characters:

function getCaret(el) {
  if (el.selectionStart) {
    return el.selectionStart;
  } else if (document.selection) {
    el.focus();

    var r = document.selection.createRange();
    if (r == null) {
      return 0;
    }

    var re = el.createTextRange(),
        rc = re.duplicate();
    re.moveToBookmark(r.getBookmark());
    rc.setEndPoint('EndToStart', re);

    return rc.text.length;
  }
  return 0;
}

Example Usage

You can utilize this function like so:

const textarea = document.getElementById('my-textarea');
const caretPosition = getCaret(textarea);

Retrieving Surrounding Strings

To obtain the strings surrounding the cursor or selection, you can leverage the substring() function to extract the text before, during, and after the selection.

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