// nested function example

​

// outer function

function greet(name) {

​

    // inner function

    function displayName() {

        console.log('Hi' + ' ' + name);

    }

​

    // calling inner function

    displayName();

}

​

// calling outer function

greet('John'); // Hi John

/*

 * A nested function is a function within another function.

 * A nested function is local, meaning it can only be accessed

 * by code within that same function scope.

 */

function globalFunction() {

    function localFunction() {

        return "Hello world!";

    }

    return localFunction();

}

console.log(globalFunction()); // -> "Hello world!"

console.log(localFunction()); // -> Uncaught ReferenceError: localFunction is not defined

/*

Function Syntax:

function functionName(parameter1, parameter2, ...) {

    return something;

}

*/

​

function globalFunction(a, b, c) {

    // `localFunction` cannot be called outside of `globalFunction`, once `globalFunction` finishes, `localFunction` ceases to exist

    function localFunction(d, e, f) {

        return [ f, e, d ];

    }

    return localFunction(a, b, c);

}

// nested function

​

let a = 10;

​

const main = () => {

  let b = 20;

  const inner = () => {

    let c = 30;

    console.log(a, b, c);

  };

​

  return inner();

};

​

main(); // 10 20 30