javascript - Parse large JSON file in Nodejs and handle each object independently

Question

I need to read a large JSON file (around 630MB) in Nodejs and insert each object to MongoDB.

I've read the answer here:Parse large JSON file in Nodejs.

However, answers there are handling the JSON file line by line, instead of handling it object by object. Thus, I still don't know how to get an object from this file and operate it.

I have about 100,000 this kind of objects in my JSON file.

Data Format:

[
  {
    "id": "0000000",
    "name": "Donna Blak",
    "livingSuburb": "Tingalpa",
    "age": 53,
    "nearestHospital": "Royal Children's Hospital",
    "treatments": {
        "19890803": {
            "medicine": "Stomach flu B",
            "disease": "Stomach flu"
        },
        "19740112": {
            "medicine": "Progeria C",
            "disease": "Progeria"
        },
        "19830206": {
            "medicine": "Poliomyelitis B",
            "disease": "Poliomyelitis"
        }
    },
    "class": "patient"
  },
 ...
]

Cheers,

Alex

Answer 1

There is a nice module named 'stream-json' that does exactly what you want.

It can parse JSON files far exceeding available memory.

and

StreamArray handles a frequent use case: a huge array of relatively small objects similar to Django-produced database dumps. It streams array components individually taking care of assembling them automatically.

Here is a very basic example:

const StreamArray = require('stream-json/streamers/StreamArray');
const path = require('path');
const fs = require('fs');

const jsonStream = StreamArray.withParser();

//You'll get json objects here
//Key is an array-index here
jsonStream.on('data', ({key, value}) => {
    console.log(key, value);
});

jsonStream.on('end', () => {
    console.log('All done');
});

const filename = path.join(__dirname, 'sample.json');
fs.createReadStream(filename).pipe(jsonStream.input);