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anchorOffset property (selectionRange)

Browser support:

9

Returns the start position of the selection relative to the anchor node.

Note: The selectionRange object and its anchorOffset property are supported in Internet Explorer from version 9.

The anchor point is the point where the process of selecting was started. The anchor node is the deepest node in the DOM hierarchy that contains the anchor point.

In most cases, the anchorNode property refers to a TextNode.
In that case, the anchorOffset property returns the character position within the text content of the anchor node, where the selection begins.
However, in some cases (for example when the entire contents of the page are selected with Ctrl+A) the anchorNode property refers to a node that can have child nodes.
In that case, the anchorOffset property returns the index in the childNodes collection of the anchor node, where the selection begins. See the example for details.

Note that if the anchor point is placed after the focus point, then the anchor point is not part of the selection (it is the first position after), therefore the value returned by the anchorOffset property can be equal to the length of the text content or childNodes collection of the anchor node.

Similarly, the focus point is the point where the process of selecting was ended. The focus node is the deepest node in the DOM hierarchy that contains the focus point. The focusOffset property returns the position of the focus point relative to the focus node.

Note that the anchorNode and focusNode properties behave differently in Opera than in other browsers. In Opera, the element returned by the anchorNode property is never placed after the element returned by the focusNode property in the DOM hierarchy. In Firefox, Google Chrome, Safari and Internet Explorer, it depends on the direction of the selection. See the example for details.

The selectionRange object represents the current selection and every Range object that belongs to the selectionRange object represents a contiguous part of the selection. You can get the Range objects that belong to the selectionRange object with the getRangeAt method. The startContainer, startOffset, endContainer and endOffset properties of the Range object are similar to the anchorNode, anchorOffset, focusNode and focusOffset properties of the selectionRange object.

In Internet Explorer, Opera, Google Chrome, Safari and Firefox before version 3, at most one Range can belong to the selectionRange object, because text selection is always a contiguous part of the DOM hierarchy. In that case, using the anchorNode, anchorOffset, focusNode and focusOffset properties of the selectionRange object is simpler than using the properties of the Range object belongs to the selectionRange object.
In Firefox from version 3, multiple areas of text can be selected by holding down the CTRL key while selecting. If multiple ranges are added to the selection (by the user or by script, see the addRange method), then use the properties of the Range objects of the selection for similar functionality.

If you need the entire selected text in one piece, use the toString method. To modify the selection, use the methods of the selectionRange object.

The properties mentioned above belong to the selectionRange object, which is not supported by Internet Explorer before version 9. If you want to get or manipulate the selection in that browsers (and optionally in newer ones as well), use the selection object with the createRange or createRangeCollection method.

Syntax:

object.anchorOffset;

You can find the related objects in the Supported by objects section below.

This property is read-only.

Possible values:

Integer that represents the position.

Default: this property has no default value.

Example HTML code 1:

The following example illustrates the use of the anchorOffset property:

<head>
    <script type="text/javascript">
        function GetOffset () {
            if (window.getSelection) {  // all browsers, except IE before version 9
                var selection = window.getSelection ();
                var offset = selection.anchorOffset;

                alert ("The selection was started at the " + offset + ". character position.");
            } else {
                alert ("Your browser does not support this example!");
            }
        }
    </script>
</head>
<body>
    <button onclick="GetOffset ();">Get start position!</button>
    <div>Select some of this text, starting at different positions and in different directions.</div>
</body>