JSON.stringify和JSON.parse

用来json和string互相转化，在数据交换中常用到；

JSON.stringify(value [, replacer] [, space])
  • 主要说的是第二个参数为转换结果的函数或者数组

数组

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var contact = new Object();
contact.firstname = "Jesper";
contact.surname = "Aaberg";
contact.phone = ["555-0100", "555-0120"];

var memberfilter = new Array();
memberfilter[0] = "surname";
memberfilter[1] = "phone";
var jsonText = JSON.stringify(contact, memberfilter, "\t");
document.write(jsonText);
// Output:
// { "surname": "Aaberg", "phone": [ "555-0100", "555-0120" ] }

函数：

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var continents = new Array();
continents[0] = "Europe";
continents[1] = "Asia";
continents[2] = "Australia";
continents[3] = "Antarctica";
continents[4] = "North America";
continents[5] = "South America";
continents[6] = "Africa";

var jsonText = JSON.stringify(continents, replaceToUpper);

function replaceToUpper(key, value) {
    return value.toString().toUpperCase();
}

//Output:
// "EUROPE,ASIA,AUSTRALIA,ANTARCTICA,NORTH AMERICA,SOUTH AMERICA,AFRICA"

  • 一个特殊用法把json里面的函数也格式化为json串

    var ss = {

    "aa":"bbb",
"bb":function(){console.log("3333")}

    }

把上面对象字符串话其方法也一块传输过去;自然想到JSON.stringify;

但stringify会过滤值为函数的key自然想到其第二个参数所以可以

JSON.stringify(ss,function(key,val){
    console.log(key,"===",val);
    if(typeof val ==="function"){
        return val.toString();
    }else{
        return val;
    }
});

输出结果：

 === Object {aa: "bbb", bb: function}
aa === bbb
bb === function (){console.log("3333")}
"{"aa":"bbb","bb":"function (){console.log(\"3333\")}"}"

看结果知道调用函数的次数为对象原属性值个数+1;

对于数据传输之后如何解析可以用下面的

JSON.parse(text [, reviver])

学习的主要是第二个参数

官方例子

var jsontext = '{ "hiredate": "2008-01-01T12:00:00Z", "birthdate": "2008-12-25T12:00:00Z" }';
var dates = JSON.parse(jsontext, dateReviver);
document.write(dates.birthdate.toUTCString());

function dateReviver(key, value) {
    var a;
    if (typeof value === 'string') {
        a = /^(\d{4})-(\d{2})-(\d{2})T(\d{2}):(\d{2}):(\d{2}(?:\.\d*)?)Z$/.exec(value);
        if (a) {
            return new Date(Date.UTC(+a[1], +a[2] - 1, +a[3], +a[4],
                            +a[5], +a[6]));
        }
    }
    return value;
};

反转上面的值：

var dddd = JSON.parse(dd,function(key,val){
    console.log(key,"===",val);//也调用n+1次,最后key为“ ”；
    if(val&&val.indexOf&&val.indexOf('function')>=0){
         return new Function("return "+val)();
    }else{
        return val;
    }

});

结果：

aa === bbb VM3687:3
bb === function (){console.log("3333")} VM3687:3
 === Object {aa: "bbb", bb: function}

Object {aa: "bbb", bb: function}

参考资料

http://msdn.microsoft.com/zh-cn/library/ie/cc836459(v=vs.94).aspx