What if we could return a function expression that in-turn returns the values array? Variables declared in a function are available to any code within the function, including self-invoking functions.

By using a self-invoking function, our dilemma is solved.

var ValueAccumulator = function() {   var values = [];   var accumulate = function(obj) {     if (obj) {       values.push(obj.value);       return values;     }     else {       return values;     }   };   return accumulate; };  //This allows us to do this: var accumulator = ValueAccumulator(); accumulator(obj1);  accumulator(obj2);  console.log(accumulator());  // Output: [obj1.value, obj2.value]

It's all about variable scoping. The values variable is available to the inner accumulate() function, even when code outside the scope calls the functions. This is called a closure.

Closures are a feature of all functional languages. Traditional imperative languages do not allow them.