Parse mongoexport dumps in an memory efficient way

mongoexport-parser.js

var fs = require('fs');

// Dump your collection with: mongoexport --collection collectionname --db dbname --out output.json --query '{ "myprop": "test" }'

var stream = fs.createReadStream("output.json", {flags: 'r', encoding: 'utf-8'});
var buf = '';

var count = 0;
stream.on('data', function(data) {
    buf += data.toString();
    while(true) {
        // Find the next record in buf
        let start = buf.indexOf('{"_id"');
        let end = buf.indexOf('}\n');
        if(start > -1 && end > start) {
            console.log(`${count++}`);
            var json = buf.substr(start, end - start + 1); // Extract record from buf
            let obj = JSON.parse(json); // Parse the JSON
            buf = buf.slice(end + 2); // Remove the record from buf
            
            // Do something with obj
        } else {
            break;
        }
    }
});