Using Node.js
sync mode:
var fs = require("fs");
var text = fs.readFileSync("./mytext.txt");
var textByLine = text.split("\n")
async mode:
var fs = require("fs");
fs.readFile("./mytext.txt", function(text){
var textByLine = text.split("\n")
});
UPDATE
As of at least Node 6, readFileSync returns a Buffer, so it must first be converted to a string in order for split to work:
var text = fs.readFileSync("./mytext.txt").toString('utf-8');
Or
var text = fs.readFileSync("./mytext.txt", "utf-8");