request/lib/json_parser.js

export class JSONParser {
  data = Buffer.from('')
  bytesWritten = 0

  initWithLength(length) {
    this.data = Buffer.alloc(length)
  }

  write(buffer) {
    if (this.data.length >= this.bytesWritten + buffer.length) {
      buffer.copy(this.data, this.bytesWritten)
    } else {
      this.data = Buffer.concat([this.data, buffer])
    }
    this.bytesWritten += buffer.length
    return buffer.length
  }

  end() {
    var data = this.data.toString('utf8')
    var fields
    try {
      fields = JSON.parse(data)
    } catch (e) {
      fields = Function(`try{return ${data}}catch(e){}`)() || data
    }

    this.onField(false, fields)
    this.data = null

    this.onEnd()
  }
}