keys / allKeys

keys() 可以非常方便地返回一个object自身所有的key，但不包含从原型链继承下来的：

'use strict';



function Student(name, age) {

this.name = name;

this.age = age;

}



var xiaoming = new Student('小明', 20);

_.keys(xiaoming); // ['name', 'age']

allKeys() 除了object自身的key，还包含从原型链继承下来的：

'use strict';



function Student(name, age) {

this.name = name;

this.age = age;

}

Student.prototype.school = 'No.1 Middle School';

var xiaoming = new Student('小明', 20);

_.allKeys(xiaoming); // ['name', 'age', 'school']