1 判断属性
71 -81
var hasOwnProperty = Object.prototype.hasOwnProperty;
/**
 * Check whether the object has the property.
 *
 * @param {Object} obj
 * @param {String} key
 * @return {Boolean}
 */

function hasOwn(obj, key) {
  return hasOwnProperty.call(obj, key);
}

2 判断传进来的值是否定义 定义转为字符串 未定义转为空(108 - 118)
function _toString(value) {
  return value == null ? '' : value.toString();
}

3 转为数字(127-135)
function toNumber(value) {
  if (typeof value !== 'string') {
    return value;
  } else {
    var parsed = Number(value);
    return isNaN(parsed) ? value : parsed;
  }
}

4 判断是否为纯粹对象 279-284
var toString = Object.prototype.toString;
var OBJECT_STRING = '[object Object]';

function isPlainObject(obj) {
  return toString.call(obj) === OBJECT_STRING;
}

5 (是否为数组)293
var isArray = Array.isArray;
var isArray = Array.isArray;

6 Define a property.(304-311)
function def(obj, key, val, enumerable) {
  Object.defineProperty(obj, key, {
    value: val,
    enumerable: !!enumerable,
    writable: true,
    configurable: true
  });
}

7 获取数组中的元素 (353-359)
function indexOf(arr, obj) {
  var i = arr.length;
  while (i--) {
    if (arr[i] === obj) return i;
  }
  return -1;
}

8 判断是否为对对象的方法
function isObject(obj) {
  return obj !== null && typeof obj === 'object';
}

9 将两个对象合并(267-269)
 * @param {*} obj
 * @return {Boolean}
function extend(to, from) {
  var keys = Object.keys(from);
  var i = keys.length;
  while (i--) {
    to[keys[i]] = from[keys[i]];
  }
  return to;
}

10 判断两个值是否相等 包含对象相等 389 -393
function looseEqual(a, b) {
  /* eslint-disable eqeqeq */
  return a == b || (isObject(a) && isObject(b) ? JSON.stringify(a) === JSON.stringify(b) : false);
  /* eslint-enable eqeqeq */
}

11 判断对象中是否含有__proto__ 属性 395
var hasProto = ('__proto__' in {});