//javascript对象
   var obj = {
    name: "liu",
    age: 33,
   };


   // json对象
   {
    "name": "liu",
    "age": 33,
   }

var str = '{"name":"huangxiaojian","age":"23"}';
console.log(JSON.parse(str)); //Object { name: "huangxiaojian", age: "23" }

var book = {
     title: "hello",
     author: [ "apple" ],
     year: 300,
     releaseDate: new Date(2016)
    };

    var jsonText = JSON.stringify( book )
    var bookCopy = JSON.parse( jsonText, function( key, value ) {
     if (key == "releaseDate" ) {
      return new Date( value );
     } else {
      return value;
     }
    } );
    console.log( bookCopy.releaseDate.getFullYear() );

var a = {a:1,b:2};
console.log(JSON.stringify(a)); //{"a":1,"b":2}不包含任何空格字符或缩进

var person = {
 name: "liu",
 age: 33,
 eat: [ "apple" ],
 sex: "man"
}
var jsonText = JSON.stringify( person, ["eat", "age" ] )
console.log( jsonText ) //{"eat":["apple"],"age":33}

 var person = {
   "name": "liu",
   "age": 33,
   "eat": [ "apple" ],
   "sex": "man"
  }
  var jsonText = JSON.stringify( person, function( key, value ) {
   // console.log( value )
   switch("eat") {
    case "eat":
    return [3,4,5,5,5].join(",");
    case "age":
    return 33;
    case "sex":
    return undefined;
    default:
    return value;            
   }
  } )
  console.log( jsonText ) //"3,4,5,5,5"

 var person = {
   "name": "liu",
   "age": 33,
   "eat": [ "apple" ],
   "sex": "man"
  }
  var jsonText = JSON.stringify( person, null, 4 ) 
  console.log( jsonText )


/////////////////////////结果，带有格式////////////////////
{
 "name": "liu",
 "age": 33,
 "eat": [
  "apple"
 ],
 "sex": "man"
}

 

  //特别的缩进方式
  var jsonText = JSON.stringify( person, null, "---" ) 
  console.log( jsonText )
/////////////////////////结果，带有格式////////////////////
{
---"name": "liu",
---"age": 33,
---"eat": [
------"apple"
---],
---"sex": "man"
}

 var date = new Date()
  console.log( date.toJSON() ) 

 //person自身没有json数据格式，这是错的。
  var person = {
   "name": "liu",
   "age": 33,
   "eat": [ "apple" ],
   "sex": "man"
  }
console.log( person.toJSON() ) 

var person = {
     "name": "liu",
     "age": 33,
     "eat": [ "apple" ],
     "sex": "man",
     "toJSON": function () {
      return this.age
     }
    }
    console.log( person.toJSON() ) // 33