What is Free Variable ?

Free variables are variables used in function that are neither locally declared

nor passed as parameter neither part of global scope.

Code:

function numberGenerator() {

// Local “free” variable that ends up within the closure

var num = 1;

function checkNumber() {

console.log(num);

}

num++;

return checkNumber;

}

var number = numberGenerator();

number(); // 2

Output:

2

Explanation:

Here num is neither local variable w.r.t. function checkNumber()

nor variable passed to function checkNumber() as parameter.

Hence num is free variable w.r.t. checkNumber() function.