selection.js

'use strict';

var get = easyGet;
var set = easySet;
var inputTag = /input/i;
var textareaTag = /textarea/i;

if (document.selection && document.selection.createRange) {
  get = hardGet;
  set = hardSet;
}

function easyGet (el) {
  return {
    start: el.selectionStart,
    end: el.selectionEnd
  };
}

function hardGet (el) {
  var active = document.activeElement;
  if (active !== el) {
    el.focus();
  }

  var range = document.selection.createRange();
  var bookmark = range.getBookmark();
  var original = el.value;
  var marker = getUniqueMarker(original);
  var parent = range.parentElement();
  if (parent === null || !inputs(parent)) {
    return result(0, 0);
  }
  range.text = marker + range.text + marker;

  var contents = el.value;

  el.value = original;
  range.moveToBookmark(bookmark);
  range.select();

  return result(contents.indexOf(marker), contents.lastIndexOf(marker) - marker.length);

  function result (start, end) {
    if (active !== el) { // don't disrupt pre-existing state
      if (active) {
        active.focus();
      } else {
        el.blur();
      }
    }
    return { start: start, end: end };
  }
}

function getUniqueMarker (contents) {
  var marker;
  do {
    marker = '@@marker.' + Math.random() * new Date();
  } while (contents.indexOf(marker) !== -1);
  return marker;
}

function inputs (el) {
  return ((inputTag.test(el.tagName) && el.type === 'text') || textareaTag.test(el.tagName));
}

function easySet (el, p) {
  el.selectionStart = special(el, p.start);
  el.selectionEnd = special(el, p.end);
}

function hardSet (el, p) {
  var range = el.createTextRange();

  if (p.start === 'end' && p.end === 'end') {
    range.collapse(false);
    range.select();
  } else {
    range.collapse(true);
    range.moveEnd('character', p.end);
    range.moveStart('character', p.start);
    range.select();
  }
}

function special (el, value) {
  return value === 'end' ? el.value.length : value || 0;
}

function selection (el, p) {
  if (arguments.length === 2) {
    set(el, p);
  }
  return get(el);
}

module.exports = selection;