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  JavaScript notes --Objects
     
  Add Date : 2017-08-31      
         
         
         
  JavaScript simple data types: numeric, string, true / false, null and undefined. All other values are objects. Arrays are objects, methods and object. Attribute value is any value other than open undefined values. JavaScript properties can change. And C # dynamic similar to dynamic class.

I. object declaration and initialization.

Notes:
1. property contains "-" and "" quotation marks when needed, for the "_" unquoted

var stooge = {
        "First Name": "Frank",
        "Last Name": "Zhang"
    } Var person = {
        name: "Frank",
        Age: 23,
 }

      II. Retrieval.

Notes:
1. retrieve the value of the object can be obtained through the [] and.

2. If the assigned time, the property does not exist. Then automatically creates the property and assigns.

3. Retrieve .propertyName if there is no output undefine;

4. Get undefine, .PropertyName null data will be given, if the data is non-null and non-undefine error will not even be assigned a number.

    console.log (person.name);

    stooge [ "middle Name"] = "C"; // attribute does not exist, re-create the property
    console.log ( "." "." "My full name is" + stooge [ "first Name"] + + stooge [ "middle Name"] + + stooge [ "last Name"]); //Frank.C. Zhang

    console.log (person.vip); // no error, output undefine
    try {
        console.log ( "test" + person.Vip.Msg); // .vip not declared, then the object will get .msg error
    } Catch (ex) {
        console.log (ex.message); // output Can not read property 'Msg' of undefined
    }
    
    person.Vip = null;
    try {
        console.log ( "test" + person.Vip.Msg); // .vip not declared, then the object will get .msg error
    } Catch (ex) {
        console.log (ex.message); // output Can not read property 'Msg' of null
    }

    person.Vip = 1;
    try {
        console.log (person.Vip.Msg); // output undefine
    } Catch (ex) {
        console.log (ex.message);
    }

III. Reflection

    console.log (person.hasOwnProperty ( "name")); // true
    console.log (typeof (person.Age)); // number
    console.log (typeof (person.toString)); // function

IV. Traversal

Notes:
1. traverse the object when, name is the name of the property instead of the corresponding property value;.

2. Obtain the property value or through [] and access.;

for (var name in stooge) {
        console.log (name);
        console.log (typeof (name));

        console.log (stooge [name]);
        console.log (typeof (stooge [name]));
    }

V. deleted.

Notes:
1. Delete Attribute removed via delete obj.propertyName.

VI. Local class

Notes: global variables in front of the class we are using the global variables used in the program will reduce the excessive flexibility, and the development will encounter duplicate naming issues namespace in C #, in Java also has package,. in fact, we can name a JavaScript object. Then package their own specific data into objects. To achieve isolation.

var MyNamespace = {};
    MyNamespace.person = {
        name: "Frank",
        Age: 23
    }

    console.log (MyNamespace.person.name);
     
         
         
         
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