@gechiui/dom/build/dom/is-selection-forward.js

DOM utilities module for GeChiUI.

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = isSelectionForward;

var _assertIsDefined = require("../utils/assert-is-defined");

/**
 * Internal dependencies
 */

/**
 * Returns true if the given selection object is in the forward direction, or
 * false otherwise.
 *
 * @see https://developer.mozilla.org/en-US/docs/Web/API/Node/compareDocumentPosition
 *
 * @param {Selection} selection Selection object to check.
 *
 * @return {boolean} Whether the selection is forward.
 */
function isSelectionForward(selection) {
  const {
    anchorNode,
    focusNode,
    anchorOffset,
    focusOffset
  } = selection;
  (0, _assertIsDefined.assertIsDefined)(anchorNode, 'anchorNode');
  (0, _assertIsDefined.assertIsDefined)(focusNode, 'focusNode');
  const position = anchorNode.compareDocumentPosition(focusNode); // Disable reason: `Node#compareDocumentPosition` returns a bitmask value,
  // so bitwise operators are intended.

  /* eslint-disable no-bitwise */
  // Compare whether anchor node precedes focus node. If focus node (where
  // end of selection occurs) is after the anchor node, it is forward.

  if (position & anchorNode.DOCUMENT_POSITION_PRECEDING) {
    return false;
  }

  if (position & anchorNode.DOCUMENT_POSITION_FOLLOWING) {
    return true;
  }
  /* eslint-enable no-bitwise */
  // `compareDocumentPosition` returns 0 when passed the same node, in which
  // case compare offsets.


  if (position === 0) {
    return anchorOffset <= focusOffset;
  } // This should never be reached, but return true as default case.


  return true;
}
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