The String.raw tag function can be used with template literals to access a version of their contents without interpreting any backslash escape sequences.

String.raw\\\\n will contain a backslash and the lowercase letter n, while \\\\n or '\\n' would contain a single newline character instead.

const patternString = String.raw`Welcome, (\\w+)!`;
const pattern = new RegExp(patternString);

const message = "Welcome, John!";
pattern.exec(message);

["Welcome, John!", "John"]