第二次理解json

// js对象和json 的区别

    var friend ={
        firstname:‘zhang‘,
        lastname:‘cl‘,
        address:null,
        // address:‘‘,
        // address:undefined,
    };
    // 
    var str = ‘{"name":"alan"}‘;

    // json 格式对象
    var json ={
        "name":"alan",
        "age":"23",
        "gender":"female",

    };
    // json 格式数组
    var arr =[
        {
        "name":"alan",
        "age":"23",
        "gender":"female",

    },
    {
        "name":"kitty",
        "age":"23",
        "gender":"female",
    },
    {
        "name":"tom",
        "age":"23",
        "gender":"male",
    }
    ]

    var json2 = JSON.parse(str);
    // json 格式的对象
    // 
    var str =  JSON.stringify(friend);
    var str2 = ‘{"firstname":"zhang","lastname":"cl","address":null}‘;
    var json3 = {"firstname":"zhang","lastname":"cl","address":null}
    // console.log(str);
    console.log(typeof(json3));