![Thirty Days Of JavaScript](../images/banners/day_1_7.png)
- [📔 Day 7](#%f0%9f%93%94-day-7)
- [📔 Day 7](#-day-7)
- [Functions](#functions)
- [Function Declaration](#function-declaration)
- [Function without a parameter and return](#function-without-a-parameter-and-return)
@ -34,7 +34,7 @@
- [Arrow Function](#arrow-function)
- [Function with default parameters](#function-with-default-parameters)
- [Function declaration versus Arrow function](#function-declaration-versus-arrow-function)
- [💻 Exercises](#%f0%9f%92%bb-exercises)
- [💻 Exercises](#-exercises)
- [Exercises: Level 1](#exercises-level-1)
- [Exercises: Level 2](#exercises-level-2)
- [Exercises: Level 3](#exercises-level-3)
@ -79,12 +79,13 @@ Function can be declared without a parameter.
**Example:**
```js
// function without parameter, a function which square a number
// function without parameter, a function which make a number square
function square() {
let num = 2
let sq = num * num
console.log(sq)
}
square() // 4
// function without parameter
@ -95,18 +96,20 @@ function addTwoNumbers() {
console.log(sum)
}
addTwoNumbers() // function has to be called to be executed by it name
addTwoNumbers() // a function has to be called by its name to be executed
```
```js
function generateFullName (){
function printFullName (){
let firstName = 'Asabeneh'
let lastName = 'Yetayeh'
let space = ' '
let fullName = firstName + space + lastName
console.log(fullName)
}
generateFullName() // calling a function
printFullName() // calling a function
```
### Function returning value
@ -114,14 +117,14 @@ addTwoNumbers() // function has to be called to be executed by it name
Function can also return values, if a function does not return values the value of the function is undefined. Let us write the above functions with return. From now on, we return value to a function instead of printing it.
```js
function generateFullName (){
function printFullName (){
let firstName = 'Asabeneh'
let lastName = 'Yetayeh'
let space = ' '
let fullName = firstName + space + lastName
return fullName
}
console.log(generateFullName())
console.log(printFullName())
```
```js
@ -170,19 +173,20 @@ function functionName(parm1, parm2) {
//code goes her
}
functionName(parm1, parm2) // during calling or invoking two arguments needed
// Function without parameter doesn't take input, so lets make a parameter with parameter
// Function without parameter doesn't take input, so lets make a function with parameters
function sumTwoNumbers(numOne, numTwo) {
let sum = numOne + numTwo
console.log(sum)
}
sumTwoNumbers(10, 20) // calling functions
// If a function doesn't return it doesn't store data, so it should return
Expression functions are anonymous functions. After we create a function without a name and with assign it to a variable. To return a value from the function we should call the variable. Look at the example below.
Expression functions are anonymous functions. After we create a function without a name and we assign it to a variable. To return a value from the function we should call the variable. Look at the example below.
```js
//Declaration function
function square(n) {
return n * n
}
console.log(square(2)) // -> 4
// Function expression
const square = function(n) {
@ -342,7 +340,7 @@ console.log(squaredNum)
Arrow function is an alternative to write a function, however function declaration and arrow function have some minor differences.
Arrow function uses arrow instead of the keyword function to declare a function. Let us see both function declaration and arrow function.
Arrow function uses arrow instead of the keyword *function* to declare a function. Let us see both function declaration and arrow function.
```js
// This is how we write normal or declaration function
@ -358,7 +356,8 @@ const square = n => {
}
console.log(square(2)) // -> 4
// if we have only one line, it can be written as follows, explicit return
// if we have only one line in the code block, it can be written as follows, explicit return
const square = n => n * n // -> 4
```
@ -503,6 +502,8 @@ console.log('Weight of an object in Newton: ', weightOfObject(100, 1.62)) // gra
### Function declaration versus Arrow function
It ill be covered in other time
🌕 You are a rising star, now you knew function . Now, you are super charged with the power of functions. You have just completed day 7 challenges and you are 7 steps a head in to your way to greatness. Now do some exercises for your brain and for your muscle.