A Jasmine matcher checking if the actual object is of the expected type

jasmine.toBeTypeOf.js

// Checks if the actual object is of the expected type;
// the string `expected` is handled case-insensitively.
//
// Example:
//     expects(123).toBeTypeOf("Number");
jasmine.Matchers.prototype.toBeTypeOf = function(expected) {
  var actual = this.actual,
      notText = this.isNot ? ' not' : '',
      objType = actual ? Object.prototype.toString.call(actual) : '';
  this.message = function() {
    return 'Expected ' + actual + notText + ' to be the type of ' + expected;
  }
  return objType.toLowerCase() === '[object ' + expected.toLowerCase() + ']';
}