ES7 Decorator test

gistfile1.js

class Foo {
  
  @returns(Number)
  init() {
    console.log('ccc');
  }
}

function returns(type) {
  return (target, name, descriptor) => {
    descriptor.value = function(val) {
      if(val.constructor !== type) {
        throw new Error('Invalid type');
      }
    }
    return descriptor;
  }
}

var foo = new Foo();
foo.init(34);