判断数据类型

type.js

//from seajs
function isType(type) {
  return function(obj) {
    return {}.toString.call(obj) == "[object " + type + "]"
  }
}

var isObject = isType("Object")
var isString = isType("String")
var isArray = Array.isArray || isType("Array")
var isFunction = isType("Function")
var isUndefined = isType("Undefined")

//from co
//plain object
function isObject(val) {
  return Object == val.constructor;
}