Difference between response.setHeader and response.writeHead?

response.setHeader() allows you only to set a singular header.

response.writeHead() will allow you to set pretty much everything about the response head including status code, content, and multiple headers.

Consider the NodeJS docs:

response.setHeader(name, value)

Sets a single header value for implicit headers. If this header already exists in the to-be-sent headers, its value will be replaced. Use an array of strings here to send multiple headers with the same name.

var body = "hello world";
response.setHeader("Content-Length", body.length);
response.setHeader("Content-Type", "text/plain");
response.setHeader("Set-Cookie", "type=ninja");
response.status(200);

response.writeHead(statusCode[, statusMessage][, headers]))

Sends a response header to the request. The status code is a 3-digit HTTP status code, like 404. The last argument, headers, are the response headers. Optionally one can give a human-readable statusMessage as the second argument.

var body = "hello world";
response.writeHead(200, {
    "Content-Length": body.length,
    "Content-Type": "text/plain",
    "Set-Cookie": "type=ninja"
});