normalizeLineEndings

Normalizes line endings in a string.

• Use String.prototype.replace() and a regular expression to match and replace line endings with the normalized version.
• Omit the second argument, normalized, to use the default value of '\r\n'.

const normalizeLineEndings = (str, normalized = '\r\n') =>
  str.replace(/\r?\n/g, normalized);

normalizeLineEndings('This\r\nis a\nmultiline\nstring.\r\n');
// 'This\r\nis a\r\nmultiline\r\nstring.\r\n'
normalizeLineEndings('This\r\nis a\nmultiline\nstring.\r\n', '\n');
// 'This\nis a\nmultiline\nstring.\n'