var fs = require('fs')
fs.readFile("your file", {encoding: 'utf8'}, function (err,data) {
var formatted = data.replace(/This is the old line/g, 'This new line replaces the old line');
fs.writeFile("your file", formatted, 'utf8', function (err) {
if (err) return console.log(err);
});
});
Try using this:
If this doesn't work, visit https://www.npmjs.com/package/replace-in-file.