D3.js以及通用JS（JavaScript）读取并解析服务器端JSON的注意事项

这个需求其实挺明确的，但是网上搜出来的教程都乱七八糟，觉得实在需要自己总结一下。

D3.js目前已经被广泛使用在数据可视化领域，随着大数据的持续发展，这个框架估计会在今后更加流行（据说其作者Mike Bostock开始全职开发了，之前是负责纽约时报数据可视化的工程师，他本人也从纽约搬家到了旧金山……）。按照这里的介绍：https://github.com/mbostock/d3/wiki/API-Reference，D3.js实际上有专门读取JSON数据的API，所以其实D3.js读服务器端发布的JSON是非常简单的事情，这里我给出一段示例代码：

d3.json("http://localhost:8080/XXXX/datasource/HTTP",
    function handle_json_data(data){
        console.log(data)
        console.log(data.results[0]);
        var series=data.results[0].series;
        var contents=series[0];
        var values=contents.values
        console.log(values);
    });

后面这些语句是我在测试过程中用来调试用的，因为实在对JS不了解，所以用这种方法稍微深入了解一下。下面针对后面这些语句进行一些讨论：

按照网上各种教程的介绍，从服务器端取到的JSON字符串应该先使用eval函数转成JS能够处理的JSON对象，如下面几篇博客：http://blog.youkuaiyun.com/beyond0851/article/details/9285771 以及 http://www.cnblogs.com/fishtreeyu/archive/2011/11/05/2237190.html ，其中第一篇博客最后的结论看得我也是醉了。

但是我们看到上面的代码中并没有转换的过程，可以认为D3.js已经封装了上述处理过程。另外，对于一些复杂的JSON结构，应该怎么样进行处理呢？我上面代码中处理的JSON数据如下所示：

{
    "results": [
        {
            "series": [
                {
                    "name": "HTTP",
                    "columns": [
                        "time",
                        "durationTime"
                    ],
                    "values": [
                        [
                            "2015-06-18T07:31:44.514Z",
                            23137050
                        ],
                        [
                            "2015-06-18T07:31:46Z",
                            200
                        ],
                        [
                            "2015-06-18T07:31:46.123Z",
                            300
                        ],
                        [
                            "2015-08-08T18:33:50.61Z",
                            763
                        ],
                        [
                            "2015-08-08T18:33:51.505Z",
                            10628
                        ],
                        [
                            "2015-08-08T18:33:53.31Z",
                            43
                        ],
                        [
                            "2015-08-08T18:34:00.223Z",
                            285
                        ],
                        [
                            "2015-08-08T18:34:02.184Z",
                            1491
                        ],
                        [
                            "2015-08-08T18:34:02.295Z",
                            43
                        ],
                        [
                            "2015-08-08T18:34:03.839Z",
                            36
                        ],
                        [
                            "2015-08-08T18:34:04.179Z",
                            1174
                        ],
                        [
                            "2015-08-09T06:33:51.622Z",
                            768
                        ],
                        [
                            "2015-08-09T06:33:52.511Z",
                            11371
                        ],
                        [
                            "2015-08-09T06:33:54.721Z",
                            42
                        ],
                        [
                            "2015-08-09T06:33:56.031Z",
                            98
                        ],
                        [
                            "2015-08-09T06:33:57.969Z",
                            33
                        ],
                        [
                            "2015-08-09T06:34:03.951Z",
                            1376
                        ]
                    ]
                }
            ]
        }
    ]
}

大家可以结合我上面的代码看一下处理过程，实际上记住一条原则就可以：字段名前面是大括号的，直接用“.”号取，有中括号的情况下，要用[0],[1]这种数组操作首先把大括号或者字段名先取出来。