json-stream-extract

Extract specific JSON fields from a readable stream using limited allocations.

// myFile.json:
// {
//   "myField": "myValue",
//   "myOtherField": "myOtherValue"
// }

const stream = fs.createReadStream('myFile.json')
const minimal = await extract(stream, {
  myField: null
})
console.log(minimal)

// {
//   myField: 'myValue'
// }

Why would I use this?

This is useful for extracting specific small fields out of large JSON blobs without suffering the large allocations required from JSON.parse. Allocations are limited to only those necessary for creating the top-level field strings and for any values that are specified for extraction.

Performance

This is roughly 2-3x slower than JSON.parse, but the reduced allocations may make that trade-off worth the cost.