Jasmine Matcher instanceof for Jasmine 2.3 & ES6

jasmine.matcher.toBeInstanceOf.js

/* eslint-env jasmine */
beforeEach(function() {
  jasmine.addMatchers({
    toBeInstanceOf: (util, customEqualityTesters) => {
      return {
        compare: (actual, expected) => {
          const pass = (actual instanceof expected);
          return {
            pass,
            message: `Expected ${actual} to ${pass ? 'not' : ''} be instance of ${expected}`,
          };
        },
      };
    },
  });
});

I've found that, at least for immutable.js Records, use of expect(myObj).toBe(jasmine.any(MyRecord)) doesn't seem to work but this does.