js private and public

p&p.js

var isHungry = true;
var mzApp = (function(isHungry) {
  
  // 此处为private，它不能被外部访问，但可以被namespace内部使用
  var foodStore = ["cake", "fish", "meat", "icecream"];

  // 此处为public
  return {
    food: [],
    people: [
      {name: "miaozi", myFood: ""},
      {name: "happyCat", myFood: ""}, 
      {name: "happyDog", myFood: ""}
    ],
    buyFood: function (idx) {
      this.food.push(foodStore[idx]);
    },
    feedPeople: function(idx) {
      if (this.food.length > 0 && isHungry) {
        this.people[idx].myFood = this.food.pop();
        console.log(this.people[idx].name + " said: I ate " + this.people[idx].myFood + ". Thanks:) I'm happy now!");
      } else if (this.food.length === 0){
        console.log("Sorry, there is no food in storage");
      } else if (!isHungry) {
        console.log("I'm not hungry! please do not feed me!")
      }
    }
  };
  
})(isHungry);

// 因为foodStore是private，所以外部无法访问它
mzApp.foodStore; // undefined
// 而其他public的东西则可以轻松使用
mzApp.buyFood(1);
mzApp.food; // ["fish"]
mzApp.feedPeople(0); // miaozi said: I ate fish. Thanks:) I'm happy now!