So far we have seen many builtin JavaScript functions. In this section, we will focus on custom functions. What is a function? Before we start making functions, lets understand what function is and why we need function?
So far we have seen many built-in JavaScript functions. In this section, we will focus on custom functions. What is a function? Before we start making functions, lets understand what a function is and why we need function?
A function is a reusable block of code or programming statements designed to perform a certain task.
A function is declared by a function keyword followed by a name, followed by parentheses (). A parentheses can take a parameter. If a function take a parameter it will be called with argument. A function can also take a default parameter. To store a data to a function, a function has to return certain data types. To get the value we call or invoke a function.
A function is declared by a function keyword followed by a name, followed by parentheses (). A parentheses can take a parameter. If a function take a parameter(s), it will be called with argument(s). A function can also take a default parameter. To store a data to a function, a function has to return certain data types. To get the value we call or invoke a function.
Function makes code:
- clean and easy to read
@ -179,7 +179,7 @@ function sumTwoNumbers(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
// If a function doesn't return a value, it doesn't store data, so it should return
function sumTwoNumbers(numOne, numTwo) {
let sum = numOne + numTwo
@ -416,8 +416,8 @@ function greetings(name = 'Peter') {
return message
}
console.log(greetings())
console.log(greetings('Asabeneh'))
console.log(greetings()) // 'Peter, welcome to 30 Days of JavaScript!'
console.log(greetings('Asabeneh')) // 'Asabeneh, welcome to 30 Days of JavaScript!'
const weightOfObject = (mass, gravity = 9.81) => mass * gravity + ' N'
console.log('Weight of an object in Newton: ', weightOfObject(100)) // 9.81 gravity at the surface of Earth
console.log('Weight of an object in Newton: ', weightOfObject(100, 1.62)) // gravity at surface of Moon
console.log('Weight of an object in Newton: ', weightOfObject(100)) // 981
// 9.81 gravity at the surface of Earth
console.log('Weight of an object in Newton: ', weightOfObject(100, 1.62)) // 162
// gravity at surface of Moon
```
### Function declaration versus Arrow function
It Will be covered in other section.
🌕 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 ahead in to your way to greatness. Now do some exercises for your brain and for your muscle.
🌕 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 ahead in to your way to greatness. Now do some exercises for your brain and for your muscle.
@ -521,10 +525,10 @@ It Will be covered in other section.
7. Area of a circle is calculated as follows: _area = π x r x r_. Write a function which calculates _areaOfCircle_
8. Circumference of a circle is calculated as follows: _circumference = 2πr_. Write a function which calculates _circumOfCircle_
9. Density of a substance is calculated as follows:_density= mass/volume_. Write a function which calculates _density_.
10. Speed is calculated by dividing the total distance covered by a moving object divided by the total amount of time taken. Write a function which calculates a speed of a moving object, _speed_.
10. Speed is calculated by dividing the total distance covered by a moving object divided by the total amount of time taken. Write a function which calculates speed of a moving object, _speed_.
11. Weight of a substance is calculated as follows: _weight = mass x gravity_. Write a function which calculates _weight_.
12. Temperature in oC can be converted to oF using this formula: _oF = (oC x 9/5) + 32_. Write a function which convert oC to oF _convertCelsiusToFahrenheit_.
13. Body mass index(BMI) is calculated as follows: _bmi = weight in Kg / (height x height) in m2_. Write a function which calculates _bmi_. BMI is used to broadly define different weight groups in adults 20 years old or older.Check if a person is _underweight, normal, overweight_ or _obese_ based the information given below.
12. Temperature in °C can be converted to °F using this formula: _°F = (°C x 9/5) + 32_. Write a function which convert °C to °F _convertCelsiusToFahrenheit_.
13. Body mass index(BMI) is calculated as follows: _bmi = weight in kg / (height x height) in $m^2$_. Write a function which calculates _bmi_. BMI is used to broadly define different weight groups in adults, 20 years old or older.Check if a person is _underweight, normal, overweight_ or _obese_ based the information given below.
- The same groups apply to both men and women.
- _Underweight_: BMI is less than 18.5
@ -532,8 +536,8 @@ It Will be covered in other section.
- _Overweight_: BMI is 25 to 29.9
- _Obese_: BMI is 30 or more
14. Write a function called _checkSeason_, it takes a month parameter and returns the season:Autumn, Winter, Spring or Summer.
15. Math.max returns its largest argument. Write a function findMax that takes three arguments and returns their maximum without using Math.max method.
14. Write a function called _checkSeason_, it takes a month parameter and returns the season:Autumn, Winter, Spring or Summer.
15. Math.max returns its largest argument. Write a function findMax that takes three arguments and returns their maximum without using Math.max() method.
```js
console.log(findMax(0, 10, 5))
@ -545,7 +549,7 @@ It Will be covered in other section.
### Exercises: Level 2
1. Linear equation is calculated as follows: _ax + by + c = 0_. Write a function which calculates value of a linear equation, _solveLinEquation_.
1. Quadratic equation is calculated as follows: _ax2 + bx + c = 0_. Write a function which calculates value or values of a quadratic equation, _solveQuadEquation_.
1. Quadratic equation is calculated as follows: _a$x^2$ + bx + c = 0_. Write a function which calculates value or values of a quadratic equation, _solveQuadEquation_.
```js
console.log(solveQuadratic()) // {0}
@ -571,7 +575,7 @@ It Will be covered in other section.
swapValues(4, 5) // x = 5, y = 4
```
1. Declare a function name _reverseArray_. It takes array as a parameter and it returns the reverse of the array (don't use method).
1. Declare a function name _reverseArray_. It takes array as a parameter and it returns the reverse of the array (don't use _Array.reverse()_method).
```js
console.log(reverseArray([1, 2, 3, 4, 5]))
@ -580,13 +584,13 @@ It Will be covered in other section.
//['C', 'B', 'A']
```
1. Declare a function name _capitalizeArray_. It takes array as a parameter and it returns the - capitalizedarray.
1. Declare a function name _capitalizeArray_. It takes array as a parameter and it returns the capitalizedarray.
1. Declare a function name _addItem_. It takes an item parameter and it returns an array after adding the item
1. Declare a function name _removeItem_. It takes an index parameter and it returns an array after removing an item
1. Declare a function name _sumOfNumbers_. It takes a number parameter and it adds all the numbers in that range.
1. Declare a function name _sumOfOdds_. It takes a number parameter and it adds all the odd numbers in that - range.
1. Declare a function name _sumOfEven_. It takes a number parameter and it adds all the even numbers in that - range.
1. Declare a function name evensAndOdds . It takes a positive integer as parameter and it counts number of evens and odds in the number.
1. Declare a function name evensAndOdds . It takes a positive integer as parameter and it counts number of evens and odds between zero and the number.
```sh
evensAndOdds(100);
@ -601,7 +605,7 @@ It Will be covered in other section.
sum(1, 2, 3, 4) // -> 10
```
1. Writ a function which generates a _randomUserIp_.
1. Write a function which generates a _randomUserIp_.
1. Write a function which generates a _randomMacAddress_
1. Declare a function name _randomHexaNumberGenerator_. When this function is called it generates a random hexadecimal number. The function return the hexadecimal number.
@ -638,7 +642,7 @@ It Will be covered in other section.
'
```
1. Write a function name_rgbColorGenerator_ and it generates rgb colors.
1. Write a function called_rgbColorGenerator_ and it generates rgb colors.
```sh
rgbColorGenerator()
@ -664,10 +668,10 @@ It Will be covered in other section.
1. Call your function _sum_, it takes any number of arguments and it returns the sum.
1. Write a function called _sumOfArrayItems_, it takes an array parameter and return the sum of all the items. Check if all the array items are number types. If not give return reasonable feedback.
1. Write a function called _average_, it takes an array parameter and returns the average of the items. Check if all the array items are number types. If not give return reasonable feedback.
1. Write a function called _modifyArray_ takes array as parameter and modifies the fifth item of the array and return the array. If the array length is less than five it return 'item not found'.
1. Write a function called _modifyArray_ takes array as parameter and modifies(capitalize) the fifth item of the array and return the array. If the array length is less than five it return 'item not found'.
sapiensFactor
2 years ago