Use strong typed functions in JavaScript (sort of)

View the gist here.

Note: no support for return type, although this would be quite simple I think

function typed (types, cb) {
  if (Object.prototype.toString.call(types) === '[object Array]' && typeof cb === "function") {
    return function () {
      var i = arguments.length, areTypesCorrect = true;

      while (i--) {
        // need to check for some literals: string/number/boolean
        var type = typeof arguments[i], arg;

        if (type === 'string') {
          arg = new String();
        } else if (type === 'number') {
          arg = new Number();
        } else if (type === 'boolean') {
          arg = new Boolean();
        } else {
          arg = arguments[i];
        }

        if ( ! (arg instanceof types[i]) ) {
          areTypesCorrect = false;
          throw new TypeError('Argument '+ (i+1) + ' "' + arguments[i] + '" is not an instance of "' + types[i] + '" ');
          break;
        }
      }

      areTypesCorrect && cb.apply(this, arguments);
    }
  } else {
    throw new TypeError('(typed): arguments given are not valid');
  }
}

// write your function like this
var myTypedFunction = typed([String, Array], function(str, arr) {
  console.log(str, arr)
});


// will work
myTypedFunction('hello', ['world']);

// will not work
myTypedFunction(false, ['world']);