关于对象的比较方法

看到一个库中关于对象的比较方法，特记录在此

/*  primitives: value1 === value2  functions: value1.toString == value2.toString  arrays: if length, sequence and values of properties are identical  objects: if length, names and values of properties are identical  compare([[1, [2, 3]], [[1, [2, 3]]); // true  compare([[1, [2, 3], 4], [[1, [2, 3]]); // false  compare({a: 2, b: 3}, {a: 2, b: 3}); // true  compare({a: 2, b: 3}, {b: 3, a: 2}); // true  compare({a: 2, b: 3, c: 4}, {a: 2, b: 3}); // false  compare({a: 2, b: 3}, {a: 2, b: 3, c: 4}); // false  compare([[1, [2, {a: 4}], 4], [[1, [2, {a: 4}]]); // true*/function compare(value1, value2) {  if (value1 === value2) {    return true;  }  if (typeof value1 != typeof value2) {    return false;  }  if (value1 !== Object(value1)) {    // non equal primitives    return false;  }  if (!value1) {    return false;  }  if (Array.isArray(value1)) {    return compareArrays(value1, value2);  }  if (({}).toString.call(value1) == '[object Object]') {    return compareObjects(value1, value2);  } else {    return compareNativeSubtypes(value1, value2);  }}function compareNativeSubtypes(value1, value2) {  // e.g. Function, RegExp, Date  return value1.toString() === value2.toString();}function compareArrays(value1, value2) {  var len = value1.length;  if (len != value2.length) {    return false;  }  var alike = true;  for (var i = 0; i < len; i++) {    if (!compare(value1[i], value2[i])) {      alike = false;      break;    }  }  return alike;}function compareObjects(value1, value2) {  var keys1 = Object.keys(value1).sort();  var keys2 = Object.keys(value2).sort();  var len = keys1.length;  if (len != keys2.length) {    return false;  }  for (var i = 0; i < len; i++) {    var key1 = keys1[i];    var key2 = keys2[i];    if (!((key1 == key2) && (compare(value1[key1], value2[key2])))) {      return false;    }  }  return true;}