es.array.sort.js

'use strict';
var $ = require('../internals/export');
var aFunction = require('../internals/a-function');
var toObject = require('../internals/to-object');
var toLength = require('../internals/to-length');
var fails = require('../internals/fails');
var internalSort = require('../internals/array-sort');
var arrayMethodIsStrict = require('../internals/array-method-is-strict');
var FF = require('../internals/engine-ff-version');
var IE_OR_EDGE = require('../internals/engine-is-ie-or-edge');
var V8 = require('../internals/engine-v8-version');
var WEBKIT = require('../internals/engine-webkit-version');

var test = [];
var nativeSort = test.sort;

// IE8-
var FAILS_ON_UNDEFINED = fails(function () {
  test.sort(undefined);
});
// V8 bug
var FAILS_ON_NULL = fails(function () {
  test.sort(null);
});
// Old WebKit
var STRICT_METHOD = arrayMethodIsStrict('sort');

var STABLE_SORT = !fails(function () {
  // feature detection can be too slow, so check engines versions
  if (V8) return V8 < 70;
  if (FF && FF > 3) return;
  if (IE_OR_EDGE) return true;
  if (WEBKIT) return WEBKIT < 603;

  var result = '';
  var code, chr, value, index;

  // generate an array with more 512 elements (Chakra and old V8 fails only in this case)
  for (code = 65; code < 76; code++) {
    chr = String.fromCharCode(code);

    switch (code) {
      case 66: case 69: case 70: case 72: value = 3; break;
      case 68: case 71: value = 4; break;
      default: value = 2;
    }

    for (index = 0; index < 47; index++) {
      test.push({ k: chr + index, v: value });
    }
  }

  test.sort(function (a, b) { return b.v - a.v; });

  for (index = 0; index < test.length; index++) {
    chr = test[index].k.charAt(0);
    if (result.charAt(result.length - 1) !== chr) result += chr;
  }

  return result !== 'DGBEFHACIJK';
});

var FORCED = FAILS_ON_UNDEFINED || !FAILS_ON_NULL || !STRICT_METHOD || !STABLE_SORT;

var getSortCompare = function (comparefn) {
  return function (x, y) {
    if (y === undefined) return -1;
    if (x === undefined) return 1;
    if (comparefn !== undefined) return +comparefn(x, y) || 0;
    return String(x) > String(y) ? 1 : -1;
  };
};

// `Array.prototype.sort` method
// https://tc39.es/ecma262/#sec-array.prototype.sort
$({ target: 'Array', proto: true, forced: FORCED }, {
  sort: function sort(comparefn) {
    if (comparefn !== undefined) aFunction(comparefn);

    var array = toObject(this);

    if (STABLE_SORT) return comparefn === undefined ? nativeSort.call(array) : nativeSort.call(array, comparefn);

    var items = [];
    var arrayLength = toLength(array.length);
    var itemsLength, index;

    for (index = 0; index < arrayLength; index++) {
      if (index in array) items.push(array[index]);
    }

    items = internalSort(items, getSortCompare(comparefn));
    itemsLength = items.length;
    index = 0;

    while (index < itemsLength) array[index] = items[index++];
    while (index < arrayLength) delete array[index++];

    return array;
  }
});