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第20章 JSON

20.1 语法

JSON的语法可以表示以下三种类型的值。

  • 简单值
  • 对象
  • 数组

20.1.1 简单值

20.1.2 对象

20.1.3 数组

20.2 解析与序列化

20.2.1 JSON对象

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        var book = {
            title:"Professional javascript",
            authors:[
                "Nicholas C.Zakas"
            ],
            edition:3,
            year:2011
        }
        var jsonText = JSON.stringify(book);
        console.log(jsonText);
        //{"title":"Professional javascript","authors":["Nicholas C.Zakas"],"edition":3,"year":2011}
        var bookCopy = JSON.parse(jsonText);
        console.log(bookCopy.title);
        //Professional javascript

20.2.2 序列化选项

1.过滤结果

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        var book = {
            title:"Professional javascript",
            authors:[
                "Nicholas C.Zakas"
            ],
            edition:3,
            year:2011
        }
        var jsonText = JSON.stringify(book,["title","edition"]);
        console.log(jsonText);
        //{"title":"Professional javascript","edition":3}

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    var book = {
            title:"Professional javascript",
            authors:[
                "Nicholas C.Zakas"
            ],
            edition:3,
            year:2011
        }
        var jsonText = JSON.stringify(book,function(key,value){
            switch (key) {
                case "authors":
                    return value.join(",");
                case "year":
                    return 5000;
                //如果函数返回了undefined，那么相应的属性会被忽略
                case "edition":
                    return undefined;
                default:
                    return value;
            }
        });
        console.log(jsonText);
        //{"title":"Professional javascript","authors":"Nicholas C.Zakas","year":5000}

2.字符串缩进

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        var book = {
            title:"Professional javascript",
            authors:[
                "Nicholas C.Zakas"
            ],
            edition:3,
            year:2011
        }
        //每个级别缩进4个空格
        var jsonText = JSON.stringify(book, null, 4);
        console.log(jsonText);
        // {
  //        "title": "Professional javascript",
  //        "authors": [
  //            "Nicholas C.Zakas"
  //        ],
  //        "edition": 3,
  //        "year": 2011
        // }

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    var book = {
            title:"Professional javascript",
            authors:[
                "Nicholas C.Zakas"
            ],
            edition:3,
            year:2011
        }

        var jsonText = JSON.stringify(book, null, "--");
        console.log(jsonText);
        // {
        // --"title": "Professional javascript",
        // --"authors": [
        // ----"Nicholas C.Zakas"
        // --],
        // --"edition": 3,
        // --"year": 2011
        // }

3.toJSON()方法

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        var book = {
            title:"Professional javascript",
            authors:[
                "Nicholas C.Zakas"
            ],
            edition:3,
            year:2011,
            toJSON:function(){
                return this.title;
            }
        }

        var jsonText = JSON.stringify(book);
        console.log(jsonText);
        //"Professional javascript"

20.2.3 解析选项

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        var book = {
            title:"Professional javascript",
            authors:[
                "Nicholas C.Zakas"
            ],
            edition:3,
            year:2011,
            releaseDate: new Date(2011,11,1)
        }

        var jsonText = JSON.stringify(book);
        console.log(jsonText);
        var bookCopy = JSON.parse(jsonText,function(key,value){
            if(key == "releaseDate"){
                return new Date(value);
            } else {
                return value;
            }
        });
        console.log(bookCopy.releaseDate.getFullYear());
        //2011
最后更新: November 9, 2021
创建日期: November 29, 2023