Question

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What is the purpose of a self executing function in javascript?
Explain JavaScript's encapsulated anonymous function syntax

for instance:

(function($) {
document.getElementById("foo").innerHTML = 'bar';
})();

I understand that we want to create our own scope to prevent variable collision but why does javascript need to have ()()?

Answer 1

That makes it a self-invoking anonymous function.

(function() { 
    /* function body */ 
}) /* <-- end of function definition */ (); // <-- invoke that function immediately