AsyncLineStream.js

class AsyncLineStream {
  constructor(stream){
    this._lines = [];
    this._readline = require('readline').createInterface({
	    input: stream
    });

    this._updateReadLinePromise();
  }

  _updateReadLinePromise(){
    this._readlinePromise = new Promise((resolve) => {
      var closer;

      this._readline.once('close', closer = () => {
        this._readlinePromise = Promise.resolve();
        resolve();
      });

      this._readline.once('line', (line) => {
        this._lines.push(line);
        this._readline.removeListener('close', closer);
        this._updateReadLinePromise();
        resolve();
      })
    })
  }

  [Symbol.asyncIterator](){
    return {
      // TODO doesn't pull lines when waiting for new lines
      next: async () => {
        await this._readlinePromise;
        var line = this._lines.shift();
        return { done: line === undefined , value: line };
      }
    };
  }
};

(async () => {
  var i = 0;
  for await (let line of new AsyncLineStream(process.stdin)) { // iterates over the arr
    console.log(line);
  }
})();