readfileLineByLine.js

const fs = require('fs');
const lineReader = require('line-reader');
const mainframeFileName = 'ftc/infolease-23-4-21.txt';
    const microserviceFileName = 'ftc/23-4-21-CACS_TO_INFOLEASE';
    var counter = 0;
    const mainframeLines = await readlinesFromFile(mainframeFileName);
    const microserviceLines = await readlinesFromFile(microserviceFileName);
    const file1rmsRecords = [];
    for (const line of mainframeLines) {
      const result = flatFileToObj(
        rmsInterfaceRecordWidthConfig,
        line,
        getRmsInterfaceRecord()
      );
      file1rmsRecords.push(result.rmsInterfaceRecord);
    }
const readlinesFromFile = (file) => {
  const lines = [];
  return new Promise((resolve, reject) => {
    lineReader.eachLine(file, (line, last) => {
      lines.push(line);
      if (last) {
        resolve(lines);
      }
    });
  });
};