How to append data in json file using typescript?-CodePudding

I have a problem appending data in my .json file. So I searched this problem and found a lot of results, but it doesn't work for me. If there is a library for comfort appending data in json file or just fix my code I will be grateful

Here is my function

function writeToJson(path: string, data: any, rewrite: boolean = false) 
{
    let old_data: any = fs.readFileSync(path)
    if(old_data.length == 0 || rewrite == true)
    {
        fs.writeFileSync(path, JSON.stringify(data, null, 4))
        return
    }
    let json_obj: any = [JSON.parse(old_data)] // without brackets it reverts an error
    json_obj.push(data)
    fs.writeFileSync(path, JSON.stringify(json_obj, null, 4))
}

and bellow is actual result .json

[
    [
        [
            [
                [
                    {
                        "price": 0.5631746759368121,
                        "timestamp": "5/4/2022, 2:06:44 AM"
                    },
                    {
                        "price": 0.5631746759368121,
                        "timestamp": "5/4/2022, 2:06:53 AM"
                    }
                ],
                {
                    "price": 0.5631746759368121,
                    "timestamp": "5/4/2022, 2:06:55 AM"
                }
            ],
            {
                "price": 0.5631746759368121,
                "timestamp": "5/4/2022, 2:06:58 AM"
            }
        ],
        {
            "price": 0.5631746759368121,
            "timestamp": "5/4/2022, 2:07:01 AM"
        }
    ],
    {
        "price": 0.5631746759368121,
        "timestamp": "5/4/2022, 2:07:04 AM"
    }
]

As a result I expect something like

{
   {
     "price": 0.5631746759368121,
     "timestamp": "5/4/2022, 2:07:04 AM"
   }
   {
     "price": 0.5631746759368121,
     "timestamp": "5/4/2022, 2:07:04 AM"
   }
   ...
   {
     "price": 0.5631746759368121,
     "timestamp": "5/4/2022, 2:07:04 AM"
   }
}

CodePudding user response：

You probably just miss to specify the encoding:

fs.readFileSync(path, "utf8")

Node.js doc of fs.readFileSync:

If the encoding option is specified then this function returns a string. Otherwise it returns a buffer.

So now you should be able to use it as expected:

interface Data {
  price: number;
  timestamp: string;
}

let old_data: string = fs.readFileSync(path, "utf8")
// ...
let json_obj: Data[] = JSON.parse(old_data) || [] // No longer need extra array; initialoze as an empty array if needed
json_obj.push(data)

CodePudding user response：

The problem was in .json file not in a function. So if you want your script works fine


function writeToJson(path: string, data: any, rewrite: boolean = false) 
{
    let old_data: any = fs.readFileSync(path)
    if(old_data.length == 0 || rewrite == true)
    {
        fs.writeFileSync(path, JSON.stringify(data, null, 4))
        return
    }
    let json_obj: any = [JSON.parse(old_data)] // without brackets it reverts an error
    json_obj.push(data)
    fs.writeFileSync(path, JSON.stringify(json_obj, null, 4))
}

make sure that your json file already starts with brackets


[
   // empty or some data
]