stream-chain/src/jsonl/stringerStream.js

Chain functions, generators, Node streams, and Web streams into a pipeline with backpressure support.

// @ts-self-types="./stringerStream.d.ts"

import {Transform} from 'node:stream';

const stringer = options => {
  let first = true,
    prefix = '',
    suffix = '',
    separator = '\n',
    emptyValue,
    replacer,
    space;
  if (options) {
    if (typeof options.prefix == 'string') prefix = options.prefix;
    if (typeof options.suffix == 'string') suffix = options.suffix;
    if (typeof options.separator == 'string') separator = options.separator;
    if (typeof options.emptyValue == 'string') emptyValue = options.emptyValue;
    replacer = options.replacer;
    space = options.space;
  }
  return new Transform({
    writableObjectMode: true,
    ...options,
    transform(value, _, callback) {
      let result = JSON.stringify(value, replacer, space);
      if (first) {
        first = false;
        result = prefix + result;
      } else {
        result = separator + result;
      }
      this.push(result);
      callback(null);
    },
    flush(callback) {
      let output;
      if (first) {
        output = typeof emptyValue == 'string' ? emptyValue : prefix + suffix;
      } else {
        output = suffix;
      }
      output && this.push(output);
      callback(null);
    }
  });
};

export default stringer;
export {stringer as stringerStream};