javaScript closures. Undefined value as input stops script. Sometimes -

playing javascript closures end question cannot reach explain.

(function() {     console.log("inside closure"); //does not work }(foo));

it not work because foo undefined. referenceerror

but if prior set var foo = undefined; works (tested on chrome , ff).

it not same undefined set undefined?

in javascript, 'undefined' 1 of primitive data types. represents type of object.

var = undefined; var b;  console.log((typeof(a))); console.log((typeof(b)));

the output undefined both cases.

if don't declare variable @ , try access it, error thrown following. tried access c not declared @ all. uncaught referenceerror: c not defined(…)

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