Functions in javaScript

Supriya

Functions

A block of code which is defined once but called at a later time.

Some functions can be defined and called at the same time.

function declaration
function call

Function Declaration

function declaration
function expression
IIFE (immediately invokable function expression)

function declaration

function fName( arg1, arg2, ...)

{

statement-1;

statement-2;

statement-3;

}

function greetTheUser(user)
{
    if(user === undefined)
    {
        user = "new user";
    }
    return (`Hello ${user}, welcome to Target`);
}

// function call

greetTheUser(); 

greetTheUser("james");

function expressions

let fName = function ( arg1, arg2, ...)

{

statement-1;

statement-2;

statement-3;

};

let greetTheUser = function(user)
{
    if(user === undefined)
    {
        user = "new user";
    }
    return (`Hello ${user}, welcome to Target`);
};

// function call

greetTheUser();

greetTheUser("audrey");

IIFE

(function (arg1, arg2, ....)

{

statement-1;

statement-2;

statement-3;

})();

(function(user)
{
    if(user === undefined)
    {
        user = "new user";
    }
    return (`Hello ${user}, welcome to Target`);
})(); // function call

Arrow Functions

(param1, param2, . . . ) => {

statement-1;

statement-2;

statement-3

. . .

}

Arrow Functions

function funName (user)
{
    if(user === undefined)
    {
        user = "new user";
    }
    return (`Hello ${user}, welcome to Target`);
}; // function defination

funName("bennie") // function call

const funName = (user) => {
    if(user === undefined)
    {
        user = "new user";
    }
    return (`Hello ${user}, welcome to Target`);
}	// function defination

funName("bennie"); // function call

Time to put those brain cells to work


let numList = [45,67,67,78,45,34,23,23,2312,7];
let sum = 0;

const cube = function(num)
            {
                return Math.pow(num,3);
            };

const add = function(num1, num2)
            {
                return num1+num2;
            };

let cubeNum = cube(add(34,45));

// Here comes the tough one....
numList.forEach(function(n){ return sum = sum + n ; });

(function(numAry, cube)
{
numAry.forEach(function(num, i)
    {
        console.log(`${num}is the current value\n`);
    });
console.log(cube);
})(numList, cube);

QUEST!!

We can put the function inside the objects

Hint: { lists and dictionaries }

Property methods

reduce() method

That previous sum of the array can be done in a single line of code, but this time using the current and the next value.

Hint: { lists }