JavaScript 对象

1. 2 ways to create Object in JavaScript

1. Literal notation is the one where we declare the object, and, at the same time, define properties and values in the object. It makes use of { }. See first one for an example.

   //Literal
   var australia = {   
   weather: "superb",   
   people: "not many of them but they're all great!",
   tourism: "a wonderful place to holiday. please visit!"};

2. Constructor notation is where we make use of the keywords new Object(). We then use dot notation to add property and values to the object. See second one for an example.

   //Constructor
   var jordan = new Object();
   jordan.weather = "hot. but so are the people!";
   jordan.people = "see above!";
   jordan.tourism = "Codecademy's dream team retreat!";

2. There are two different ways that we can retrieve an object's properties: dot and bracket notation.

1. Dot notation: obj.myProp
2. Bracket notation: obj["myProp"]   (You can also use variable in bracket notation.

3. Functions in object are called Method.

4. this keyword: Why is using the this keyword helpful? Imagine we have a method that has a lot of complicated code and references an object's properties. We also want many objects to have this method. We can create a single generic method that uses the this keyword. Now many objects can use this method by defining a method that simply equals this generic method.

使用this，就可以不指定特定对象名称。任何一个调用该对象的实例，都可以使用这个属性或方法。

this也只能用在对象中！
所以当你在对象以外调用时，需要用objectName.functionName，在对象内，则可使用this.functionName。