Difference between res.setHeader and res.header in node.js

Question

What is the difference between res.setHeader and res.header. Which one should be used for enabling CORS? In some pages res.header is used and some pages res.setHeader is used for CORS.

Answer 1

res.setHeader() is a native method of Node.js and res.header() is an alias of res.set() method from Express framework.

Documentation: res.setHeader(), res.set()

This two methods do exactly the same thing, set the headers HTTP response. The only difference is res.setHeader() allows you only to set a singular header and res.header() will allow you to set multiple headers. So use the one fit with your needs.

Answer 2

Perhaps an example can clarify more:

// single field is set 
res.setHeader('content-type', 'application/json');

// multiple files can be set
res.set({
     'content-type': 'application/json',
     'content-length': '100',
     'warning': "with content type charset encoding will be added by default"
  });

Answer 3

Addition to high-voting answers, set is alias header which calls setHeader to set a header. here is the source code:

res.set =
res.header = function header(field, val) {
  if (arguments.length === 2) {
    var value = Array.isArray(val)
      ? val.map(String)
      : String(val);

    // add charset to content-type
    if (field.toLowerCase() === 'content-type') {
      if (Array.isArray(value)) {
        throw new TypeError('Content-Type cannot be set to an Array');
      }
      if (!charsetRegExp.test(value)) {
        var charset = mime.charsets.lookup(value.split(';')[0]);
        if (charset) value += '; charset=' + charset.toLowerCase();
      }
    }

    this.setHeader(field, value);
  } else {
    for (var key in field) {
      this.set(key, field[key]);
    }
  }
  return this;
};

Also see GitHub here