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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?
295
This is a standard JavaScript error when trying to call a function before it is defined. This error occurs if you try to execute a function that is not initialized or is not initialized correctly. This means that the expression did not return a function 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.
78
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.
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