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Asked: 2026-05-17T21:21:39+00:00

The code is as follows: <body> <a href="javascript:;" id="test">hello</a> </body> <script type="text/javascript"> document.getElementById("test").addEventListener("click", function

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The code is as follows:

<body>
    <a href="javascript:;" id="test">hello</a>
</body>

<script type="text/javascript">
    document.getElementById("test").addEventListener("click", function () {
      test()
    }, false)
    function test() {
      var postTypes = new Array('hello', 'there')
      (function() { alert('hello there') })()
    }
</script>

This will throw an:

"Uncaught TypeError: object is not a function"

If I wrap the anonymous function call/invocation in another set of parentheses it will execute the alert, but still give me an error. If I put a semicolon after the "var postTypes" definition then it will be completely fine.

I was led to believe that JavaScript does not require semicolons, so I’m making a guess that there is some weird associativity rules of function application that I am not fully understanding. Why am I getting this error?

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1 Answer

  1. Editorial Team

    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.

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