dom-seek/lib/index.js

Text traversal for HTML documents.

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports["default"] = seek;
var E_END = 'Iterator exhausted before seek ended.';
var E_SHOW = 'Argument 1 of seek must use filter NodeFilter.SHOW_TEXT.';
var E_WHERE = 'Argument 2 of seek must be an integer or a Text Node.';
var DOCUMENT_POSITION_PRECEDING = 2;
var SHOW_TEXT = 4;
var TEXT_NODE = 3;

function seek(iter, where) {
  if (iter.whatToShow !== SHOW_TEXT) {
    var error; // istanbul ignore next

    try {
      error = new DOMException(E_SHOW, 'InvalidStateError');
    } catch (_unused) {
      error = new Error(E_SHOW);
      error.code = 11;
      error.name = 'InvalidStateError';

      error.toString = function () {
        return "InvalidStateError: ".concat(E_SHOW);
      };
    }

    throw error;
  }

  var count = 0;
  var node = iter.referenceNode;
  var predicates = null;

  if (isInteger(where)) {
    predicates = {
      forward: function forward() {
        return count < where;
      },
      backward: function backward() {
        return count > where || !iter.pointerBeforeReferenceNode;
      }
    };
  } else if (isText(where)) {
    var forward = before(node, where) ? function () {
      return false;
    } : function () {
      return node !== where;
    };

    var backward = function backward() {
      return node !== where || !iter.pointerBeforeReferenceNode;
    };

    predicates = {
      forward: forward,
      backward: backward
    };
  } else {
    throw new TypeError(E_WHERE);
  }

  while (predicates.forward()) {
    node = iter.nextNode();

    if (node === null) {
      throw new RangeError(E_END);
    }

    count += node.nodeValue.length;
  }

  if (iter.nextNode()) {
    node = iter.previousNode();
  }

  while (predicates.backward()) {
    node = iter.previousNode();

    if (node === null) {
      throw new RangeError(E_END);
    }

    count -= node.nodeValue.length;
  }

  if (!isText(iter.referenceNode)) {
    throw new RangeError(E_END);
  }

  return count;
}

function isInteger(n) {
  if (typeof n !== 'number') return false;
  return isFinite(n) && Math.floor(n) === n;
}

function isText(node) {
  return node.nodeType === TEXT_NODE;
}

function before(ref, node) {
  return ref.compareDocumentPosition(node) & DOCUMENT_POSITION_PRECEDING;
}
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