How to remove line breaks and make single line text?

Question

I have a log file where events are in multiple lines. In order to make event into single line, first I have to separate lines that contain date and lines from those that are without date. Now I am trying to write a logic to check a line and if it doesn't have date, merge it with prevLine .

How can I combine multiples lines into one using regular expression or any other module that helps to achieve this task?

ctrl.js

var regex = /\[\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}\w+\]/;
var prevLine;
var readStream = fs.createReadStream(dir + '/' + logFile,'utf8');
        readStream.pipe(split()).on('data', function (line) {
            if (regex.test(line)) {
                    console.log('Line with date:', line);
                    parseLog(line,prevLine);
                } else {
                    console.log('Line without date:', line);
                    line = prevLine + line;
                }
                function parseLog(line, prev) {
                    if (line.indexOf('|') === -1) line = prev + line;
                 }
          });

fileData

[2017-03-23T18:13:16Z]|verbose|bmid: n/a|infra.topicWorkers|topology changed, emitting topology event { newTopology: 
   [ '-0000001337',
     '-0000001338',
     '-0000001339',
     '-0000001340',
     '-0000001341',
     '-0000001342' ],
  oldTopology: 
   [ '-0000001337',
     '-0000001338',
     '-0000001339',
     '-0000001340',
     '-0000001341' ],
  workerId: 6,
  pid: 30488 }
[2017-03-23T18:13:16Z]|verbose|bmid: n/a|infra.topicWorkers|topology changed, emitting topology event { newTopology: 
   [ '-0000001337',
     '-0000001338',
     '-0000001339',
     '-0000001340',
     '-0000001341',
     '-0000001342' ],
  oldTopology: [],
  workerId: 4,
  pid: 30481 }

Answer 1

You can do something like this:

const split = require('split');
const regex = /\[\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}\w+\]/;
let items = [];
let item = [];
fs.createReadtStream(path.join(dir, logFile), 'utf8')
  .pipe(split()).on('data', (line) => {
    if (regex.test(line)) {
        item = [];
        items.push(item);
    }
    item.push(line);
});
let lines = items.map(item => item.join(' '));
lines.forEach(line => console.log(line));

You can add a new line to an array every time there is a new line, but when there is a line with a date then you can put that array into another array and create a new array for those single lines. Then you can combine the elements within the inner arrays by joining them and you will have a large array of combined lines - the array called lines in that example.