JavaScript “Uncaught TypeError: object is not a function” associativity question

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 ;.

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^* 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.