如何在 Node Js 中写入文件时将 object 推入数组中

Question

How to push object inside an array while writing to a file in Node Js? I currently have the following working code

fs.appendFile("sample.json", JSON.stringify(data, undefined, 2) + ",");

where data is an object, like

{
name:'abc',
age: 22,
city: 'LA'
}

Upon appending, which results the following

{
name:'abc',
age: 22,
city: 'LA'
},
{
name:'def',
age: 25,
city: 'MI'
},

I see 2 problems here. 1. The trailing comma at the end 2. The inability to form an array and push the object into it

Any leads would be appreciated

Answer 1

Append will append your data to a file and here data is being treated as a string and all appends will be equal to concating string to another string.

Instead, here the file needs to be read first and converted to a data-structure for this example it can be an array of objects and convert that data-structure to string and write it to file.

To write to the file

fs.writeFileSync('sample.json', JSON.stringify([data], null, 2));

sample.json

[
  {
    "name": "abc",
    "age": 22,
    "city": "LA"
  }
]

Read from file

const fileData = JSON.parse(fs.readFileSync('sample.json'))
fileData.push(newData)

Write the new data appended to previous into file

fs.writeFileSync('sample.json', JSON.stringify(fileData, null, 2));

sample.json

[
  {
    "name": "abc",
    "age": 22,
    "city": "LA"
  },
  {
    "name": "abc",
    "age": 22,
    "city": "LA"
  }
]