Javascript "Uncaught TypeError: object is not a function" associativity question

Your code experiences a case where the automatic semicolon insertion (ASI) process doesn't happen.

You should never rely on ASI. You should use semicolons to properly separate statements:

var postTypes = new Array('hello', 'there'); // <--- Place a semicolon here!!

(function() { alert('hello there') })();

Your code was actually trying to invoke the array object.

JavaScript does require semicolons. It's just that the interpreter will insert them for you on line breaks where possible^*.

Unfortunately, the code

var a = new B(args)(stuff)()

does not result in a syntax error, so no ; will be inserted. (An example which can run is

var answer = new Function("x", "return x")(function(){return 42;})();

To avoid surprises like this, train yourself to always end a statement with ;.

---

^* This is just a rule of thumb and not always true. The insertion rule is much more complicated. This blog page about semicolon insertion has more detail.

I ran into this problem in React: I tried to destructure and use a named export when it was a default export, for example:

// module.js
const myFunction = () => null
export default myFunction

// component.js
// THIS WAS WRONG:
// import { myFunction } from './module'
// SHOULD BE THIS:
import myFunction from './module'