1. js区分大小写；

2. 判断自有属性使用hasOwnProperty方法；

var xiaoming = {
    name : 'xiaoming',
    age : 30,
}

console.log(xiaoming);
console.log(xiaoming.age);
console.log('tostring' in xiaoming); //false
console.log('toString' in xiaoming); //true
console.log(xiaoming.hasOwnProperty('toString')); // false