type OutputFormat = 'csv' | 'ndjson'

abstract class Output<Format extends OutputFormat> {

format: Format

constructor(format: string) {

this.format = format

}

abstract encode(data: any[]): string

}

class CSV extends Output<'csv'> {

constructor() {

super('csv')

}

encode(data: any[]) {

return data.map((row) => row.join(',')).join('\n')

}

}

class NDJSON extends Output<'ndjson'> {

constructor() {

super('ndjson')

}

encode(data: any[]) {

return data.map((row) => JSON.stringify(row)).join('\n')

}

}

function getOutput<F extends 'csv' | 'ndjson'>(format: F): Output<F> {

switch (format) {

case 'csv': return new CSV()

case 'ndjson': return new NDJSON()

}

}

Parametrized classes