JavaScript Closures

• JavaScript variables can belong to the local or global scope.
• Global variables can be made local (private) with closures.

• a closure is one way of supporting first class functions, it is an expression that can reference variables within its scope (when it was first declared), be assigned to a variable, be passed as an argument to a function, or be returned as a function result. Or

• a closure is a stack frame which is allocated when a function starts its execution, and not freed after the function returns.

example -

var add = (function () {

    var counter = 0;

    return function () {return counter += 1;}

})();

add();

add();

add();

// the counter is now 3

What I learnt in Lab class..

Create a separate function using JavaScript closure which accepts the tax percentage and

returns a function which accepts the amount and returns the amount after adding tax

percentage.

// closure is used to hide the inner implementation

function tax (taxPercentage){

    var tPer = taxPercentage; // assinging the parameter to a variable

    //outer function implementation

    return function netTax (amount) //it is like a function inside a function

    {

        var nTax = amount+tPer; // net tax is calculated adding the parameters

        return nTax;

    };

}

var f1 = tax(20); //calling the tax  method

console.log(f1(30));