javascript - 向 .json 文件添加另一个条目。 NodeJS

Question

我正在使用 JSON 文件来存储一些数据，这是我当前的结构。由我的代码尝试创建。

 {
  "Username": "ozziep",
  "ProjectID": "ExpressJS",
  "TimeStamp": "2016-12-30T19:54:52.418Z",
  "Comments": "hello world how are we today?"
}

{
  "Username": "alex",
  "ProjectID": "Foo",
  "TimeStamp": "2016-12-30T19:55:07.138Z",
  "Comments": "we need to double check that this json system works. "
}

我是这样生成JSON的，不是最好的代码，还在学习JS。

var time = new Date();
    var project_id = data.postid;
    var comment = data.commentdata;
    var usercommented = data.usercoment
    fs.readFile("comments.json", 'utf-8', function(err, data) {
            if (err) {
                throw err;
            }
            if (typeof data !== "undefined") {
      var jsongrid = {
        "Username": usercommented,
        "ProjectID": project_id,
        "TimeStamp": time,
        "Comments": comment
      }
      //this all works, for now. and will hopefully stay that way.
      console.log(commentsdata)
      var JSONStringed = JSON.stringify(jsongrid, null, 4) //turning the json grid into JSON, and prettyprinting it. generates correct JSON
                var commentsdata = data; //current JSON on file.
      var CompiledJSON = "\n"+commentsdata + "\n "+JSONStringed;//adding the new to the old.
      var bCompiledJSON = "["+CompiledJSON+"\n]"
      fs.truncate('comments.json', 0, function(){console.log('comments file can now be written to.')})



    var time = new Date();
    var project_id = data.postid;
    var comment = data.commentdata;
    var usercommented = data.usercoment
    fs.readFile("comments.json", 'utf-8', function(err, data) {
            if (err) {
                throw err;
            }
            if (typeof data !== "undefined") {
      var jsongrid = {
        "Username": usercommented,
        "ProjectID": project_id,
        "TimeStamp": time,
        "Comments": comment
      }
      //this all works, for now. and will hopefully stay that way.
      console.log(commentsdata)
      var JSONStringed = JSON.stringify(jsongrid, null, 4) //turning the json grid into JSON, and prettyprinting it. generates correct JSON
                var commentsdata = data; //current JSON on file.
      var CompiledJSON = "\n"+commentsdata + "\n "+JSONStringed;//adding the new to the old.
      var bCompiledJSON = "["+CompiledJSON+"\n]"
      fs.truncate('comments.json', 0, function(){console.log('comments file can now be written to.')})

    //  var jsonsearched = CompiledJSON.hasOwnProperty("Vortex.API")
      console.log(CompiledJSON[2])
    //  var CompiledJsonPretty = JSON.stringify(CompiledJSON, null, 4); //pretty printing this creation.
                console.log("A user has submitted a comment to post " + project_id) //logging.
                console.log("Generating JSON")
      console.log(CompiledJSON)
      socket.emit("added_comment")

                    //  var json_temp = {"Comments":{"Username":usercommented,"CommentData":comment,"date":time,"ProjectID":project_id}}
                    //var jsondata = JSON.stringify(json_temp)


                console.log("--------------------------------------------")
                console.log("Temp JSON generated - value: \n\n" + JSONStringed)
                if (typeof JSONStringed !== "undefined") {
                    fs.writeFile("comments.json", bCompiledJSON, function(err) {
                        if (!err) {
                            //verify data has been written, cause comments are important!
                            fs.readFile("comments.json", 'utf-8', function(err, data) {
                                if (err) {
                                    throw err;
                                }
                                if (data !== CompiledJSON) {
                                    console.log("Writing comment JSON to file failed.")
                                    console.log("- \n if (data) !== JSONStringed; failed. ")
                                } else{
                socket.emit("added_comment")
              }
                            })
                        } else {
                            throw err;
                        }
                    })
                }
            }
        })
        //  console.log(JSON.stringify(json))
})

我确实计划将其最小化一点，对于如此简单的事情来说，代码太多了，无论如何，它都会从 jsongrid 写入文件创建 JSON，但唯一的问题是它将它们写在彼此之上，如下所示如上所示，这不起作用，因为我无法按名称或其他方式挑选出一个 block ，我尝试读取文件，删除它，向其中添加 [] ，然后写入JSON 再次文件，但这只是添加了很多 [] 周围，这也不起作用，我想访问 JSON 中的数据，例如 foo[1].Username 例如。实现这一目标的最佳方法是什么？

Answer 1

最简单的解决方案是在文件中存储 JSON 对象数组。

请记住，虽然 JSON 代表“JavaScript 对象表示法”，但数组也是有效的 JSON。所以你的文件可能如下所示:

[
  {
    "Username": "ozziep",
    "ProjectID": "ExpressJS",
    "TimeStamp": "2016-12-30T19:54:52.418Z",
    "Comments": "hello world how are we today?"
  },
  {
    "Username": "alex",
    "ProjectID": "Foo",
    "TimeStamp": "2016-12-30T19:55:07.138Z",
    "Comments": "we need to double check that this json system works. "
  }
]

然后，要在文件中添加、删除、查找对象，您可以读取整个文件，解析它，然后执行您需要的操作。

添加评论:

var time = new Date();
var project_id = data.postid;
var comment = data.commentdata;
var usercommented = data.usercoment
// Read in whole file
fs.readFile("comments.json", 'utf-8', function(err, data) {
    if (err) {
        throw err;
    }
    if (typeof data !== "undefined") {
        // Parse the current contents of the file into array
        var currentComments = JSON.parse(data);

        // Create our new comment
        var newComment = {
            "Username": usercommented,
            "ProjectID": project_id,
            "TimeStamp": time,
            "Comments": comment
        };

        // Push it onto the end of the existing comments
        currentComments.push(newComment);

        // Convert comments back to string to be written
        var stringifiedComments = JSON.stringify(currentComments);

        // Write back to file!
        fs.writeFile("comments.json", stringifiedComments, function (err) {
            console.log(err);
        });
    }
}