How to split string with newline ('\n') in Node?

Within Node, how do I split a string using newline ('\n') ? I have a simple string like var a = "test.js\nagain.js" and I need to get ["test.js", "again.js"]. I tried

a.split("\n");
a.split("\\n");
a.split("\r\n");
a.split("\r");

but the above doesn't work.

Try splitting on a regex like /\r?\n/ to be usable by both Windows and UNIX systems.

> "a\nb\r\nc".split(/\r?\n/)
[ 'a', 'b', 'c' ]

If the file is native to your system (certainly no guarantees of that), then Node can help you out:

var os = require('os');

a.split(os.EOL);

This is usually more useful for constructing output strings from Node though, for platform portability.

It looks like regex /\r\n|\r|\n/ handles CR, LF, and CRLF line endings, their mixed sequences, and keeps all the empty lines inbetween. Try that!

    function splitLines(t) { return t.split(/\r\n|\r|\n/); }

    // single newlines
    console.log(splitLines("AAA\rBBB\nCCC\r\nDDD"));
    // double newlines
    console.log(splitLines("EEE\r\rFFF\n\nGGG\r\n\r\nHHH"));
    // mixed sequences
    console.log(splitLines("III\n\r\nJJJ\r\r\nKKK\r\n\nLLL\r\n\rMMM"));

You should get these arrays as a result:

[ "AAA", "BBB", "CCC", "DDD" ]
[ "EEE", "", "FFF", "", "GGG", "", "HHH" ]
[ "III", "", "JJJ", "", "KKK", "", "LLL", "", "MMM" ]

You can also teach that regex to recognize other legit Unicode line terminators by adding |\xHH or |\uHHHH parts, where H's are hexadecimal digits of the additional terminator character codepoint (as seen in Wikipedia article as U+HHHH).

a = a.split("\n");

---

Note that splitting returns the new array, rather than just assigning it to the original string. You need to explicitly store it in a variable.

A solution that works with all possible line endings including mixed ones and keeping empty lines as well can be achieved using two replaces and one split as follows

text.replace(/\r\n/g, "\r").replace(/\n/g, "\r").split(/\r/);

some code to test it

  var CR = "\x0D";  //   \r
  var LF = "\x0A";  //   \n

  var mixedfile = "00" + CR + LF +            // 1 x win
                  "01" + LF +                 // 1 x linux
                  "02" + CR +                 // 1 x old mac
                  "03" + CR + CR +            // 2 x old mac
                  "05" + LF + LF +            // 2 x linux
                  "07" + CR + LF + CR + LF +  // 2 x win
                  "09";
                   
  function showarr (desc, arr)
  {
     console.log ("// ----- " + desc);
     for (var ii in arr)
        console.log (ii + ") [" + arr[ii] +  "] (len = " + arr[ii].length + ")");
  }

  showarr ("using 2 replace + 1 split", 
           mixedfile.replace(/\r\n/g, "\r").replace(/\n/g, "\r").split(/\r/));

and the output

  // ----- using 2 replace + 1 split
  0) [00] (len = 2)
  1) [01] (len = 2)
  2) [02] (len = 2)
  3) [03] (len = 2)
  4) [] (len = 0)
  5) [05] (len = 2)
  6) [] (len = 0)
  7) [07] (len = 2)
  8) [] (len = 0)
  9) [09] (len = 2)

The first one should work:

> "a\nb".split("\n");
[ 'a', 'b' ]
> var a = "test.js\nagain.js"
undefined
> a.split("\n");
[ 'test.js', 'again.js' ]

I made an eol module for working with line endings in node or browsers. It has a split method like

var lines = eol.split(text)