Get caret position in HTML input?

The following will get you the start and end of the selection as character indices. It works for text inputs and textareas, and is slightly complicated because of IE's strange handling of line breaks.

function getInputSelection(el) {
    var start = 0, end = 0, normalizedValue, range,
        textInputRange, len, endRange;

    if (typeof el.selectionStart == "number" && typeof el.selectionEnd == "number") {
        start = el.selectionStart;
        end = el.selectionEnd;
    } else {
        range = document.selection.createRange();

        if (range && range.parentElement() == el) {
            len = el.value.length;
            normalizedValue = el.value.replace(/\r\n/g, "\n");

            // Create a working TextRange that lives only in the input
            textInputRange = el.createTextRange();
            textInputRange.moveToBookmark(range.getBookmark());

            // Check if the start and end of the selection are at the very end
            // of the input, since moveStart/moveEnd doesn't return what we want
            // in those cases
            endRange = el.createTextRange();
            endRange.collapse(false);

            if (textInputRange.compareEndPoints("StartToEnd", endRange) > -1) {
                start = end = len;
            } else {
                start = -textInputRange.moveStart("character", -len);
                start += normalizedValue.slice(0, start).split("\n").length - 1;

                if (textInputRange.compareEndPoints("EndToEnd", endRange) > -1) {
                    end = len;
                } else {
                    end = -textInputRange.moveEnd("character", -len);
                    end += normalizedValue.slice(0, end).split("\n").length - 1;
                }
            }
        }
    }

    return {
        start: start,
        end: end
    };
}

var textBox = document.getElementById("textBoxId");
textBox.focus();
alert( getInputSelection(textBox).start );

There is now a nice jQuery plugin for this: Caret plugin

Then you can just call $("#myTextBox").caret();


-> selectionStart

<!doctype html>
    
<html>
  <head>
    <meta charset = "utf-8">

    <script type = "text/javascript">
      window.addEventListener ("load", function () {
        var input = document.getElementsByTagName ("input");
        
        input[0].addEventListener ("keydown", function () {
          alert ("Caret position: " + this.selectionStart);
          
          // You can also set the caret: this.selectionStart = 2;
        });
      });
    </script>
    
    <title>Test</title>
  </head>

  <body>
    <input type = "text">
  </body>
</html>

Tags:

Javascript

Html

Caret

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