- [Creating a time object](#creating-a-time-object)
- [Getting full year](#getting-full-year)
- [Getting month](#getting-month)
- [Getting date](#getting-date)
- [Getting day](#getting-day)
- [Getting hours](#getting-hours)
- [Getting minutes](#getting-minutes)
- [Getting seconds](#getting-seconds)
- [Getting time](#getting-time)
- [Creating a Time Object](#creating-a-time-object)
- [Getting Full Year](#getting-full-year)
- [Getting Month](#getting-month)
- [Getting Date](#getting-date)
- [Getting Day](#getting-day)
- [Getting Hours](#getting-hours)
- [Getting Minutes](#getting-minutes)
- [Getting Seconds](#getting-seconds)
- [Getting Time](#getting-time)
- [💻 Day 3: Exercises](#-day-3-exercises)
- [Exercises: Level 1](#exercises-level-1)
- [Exercises: Level 2](#exercises-level-2)
@ -55,7 +55,7 @@
## Booleans
A boolean data type represents one of the two values:_true_ or _false_. Boolean value is either true or false. The use of these data types will be clear when you start the comparison operator. Any comparisons return a boolean value which is either true or false.
A boolean data type represents one of the two values:_true_ or _false_. The use of these data types will be clear when you start the comparison operator. Any comparisons return a boolean value, true or false.
We agreed that boolean values are either true or false.
### Truthy values
### Truthy Values
- All numbers(positive and negative) are truthy except zero
- All strings are truthy
- The boolean true
### Falsy values
### Falsy Values
- 0
- 0n
@ -84,13 +84,13 @@ We agreed that boolean values are either true or false.
- undefined
- NaN
- the boolean false
- '', "", ``, empty string
- '', "", ``, empty strings
It is good to remember those truthy values and falsy values. In later section, we will use them with conditions to make decision.
It is good to remember those truthy values and falsy values. In later sections, we will use them with conditions to make decisions.
## Undefined
If we declare a variable and if we do not assign a value, the value will be undefined. In addition to this, if a function is not returning the value will be undefined.
If we declare a variable and we do not assign it a value, the value will be undefined. In addition to this, if a function is not returning a value, it will also be undefined.
```js
let firstName
@ -106,9 +106,9 @@ console.log(empty) // -> null , means no value
## Operators
### Assignment operators
### Assignment Operators
An equal sign in JavaScript is an assignment operator. It uses to assign a variable.
An equal sign in JavaScript is an assignment operator. It is used to assign a value to a variable.
```js
let firstName = 'Asabeneh'
@ -128,7 +128,7 @@ Arithmetic operators are mathematical operators.
Try to understand the above comparisons with some logic. Remember without any logic might be difficult.
JavaScript is somehow a wired kind of programming language. JavaScript code run and give you a result but unless you are good at it may not be the desired result.
Try to understand the above comparisons with some logic. Remember without any logic it might be difficult.
JavaScript is somehow a wired kind of programming language. JavaScript code runs and gives you a result, but unless you are good at it, may not be the desired result.
As rule of thumb, if a value is not true with == it will not be equal with ===. Using === is safer than using ==. The following [link](https://dorey.github.io/JavaScript-Equality-Table/) has an exhaustive list of comparison of data types.
As rule of thumb, if a value is not true with == it will not be equal with ===. Using === is safer than using ==. The following [link](https://dorey.github.io/JavaScript-Equality-Table/) has an exhaustive list of comparisons of data types.
### Logical Operators
The following symbols are the common logical operators:
&&(ampersand) , ||(pipe) and !(negation).
&&(ampersand) , ||(pipe) and !(negation).
&& gets true only if the two operands are true.
|| gets true either of the operand is true.
|| gets true if either one of the operands is true.
In JavaScrip we use the increment operator to increase a value stored in a variable. The increment could be pre or post increment. Let us see each of them:
In JavaScrip we use the increment operator to increase a value stored in a variable. The increment could be pre or post increment. Let us see each one of them:
1. Pre-increment
@ -262,7 +262,7 @@ console.log(++count) // 1
console.log(count) // 1
```
1. Post-increment
2. Post-increment
```js
let count = 0
@ -270,11 +270,11 @@ console.log(count++) // 0
console.log(count) // 1
```
We use most of the time post-increment. At leas you should remember how to use post-increment operator.
We use most of the time post-increment. You should at least remember how to use post-increment operator.
### Decrement Operator
In JavaScrip we use the decrement operator to decrease a value stored in a variable. The decrement could be pre or post decrement. Let us see each of them:
In JavaScript we use the decrement operator to decrease a value stored in a variable. The decrement could be pre or post decrement. Let us see each one of them:
1. Pre-decrement
@ -337,9 +337,9 @@ I would like to recommend you to read about operator precendence from this [link
## Window Methods
### Window alert() method
### Window Alert() Method
As you have seen at very beginning alert() method displays an alert box with a specified message and an OK button. It is a builtin method and it takes on argument.
As you have seen at very beginning, alert() method displays an alert box with a specified message and an OK button. It is a built-in method and it takes one argument optionally.
```js
alert(message)
@ -349,11 +349,11 @@ alert(message)
alert('Welcome to 30DaysOfJavaScript')
```
Do not use too much alert because it is destructing and annoying, use it just for to test.
Do not use alert() too much, because it is destructing and annoying, use it just for testing.
### Window prompt() method
### Window Prompt() Method
The window prompt methods display a prompt box with an input on your browser to take input values and the input data can be stored in a variable. The prompt() method takes two arguments. The second argument is optional.
The window prompt method displays a prompt box with an input on your browser, to take input values. The input data can be stored in a variable. The prompt() method takes two arguments. The second argument is optional.
```js
prompt('required text', 'optional text')
@ -364,10 +364,10 @@ let number = prompt('Enter number', 'number goes here')
console.log(number)
```
### Window confirm() method
### Window Confirm() Method
The confirm() method displays a dialog box with a specified message, along with an OK and a Cancel button.
A confirm box is often used to ask permission from a user to do something. Window confirm() takes an string as an argument.
A confirm box is often used to ask permission from a user to do something. Window confirm() takes a string as an argument.
Clicking the OK yields true value, clicking the Cancel button yields false value.
```js
@ -375,16 +375,16 @@ const agree = confirm('Are you sure you like to delete? ')
console.log(agree) // result will be true or false based on what you click on the dialog box
```
These are not all the window methods we will have a separate section to go deep into window methods.
These are not all the window methods. We will have a separate section to go deep into window methods.
## Date Object
Time is an important thing. We like to know the time a certain activity or event. In JavaScript current time and date is created using JavaScript Date Object. The object we create using Date object provides many methods to work with date and time.The methods we use to get date and time information from a date object values are started with a word _get_ because it provide the information.
Time is an important thing. We like to know the time of certain activities or events. In JavaScript current time and date is created using JavaScript Date Object. The object we create using Date object provides many methods to work with date and time.The methods we use to get date and time information from a date object start with a word _get_.
🌕 You have boundless energy. You have just completed day 3 challenges and you are three steps ahead in to your way to greatness. Now do some exercises for your brain and for your muscle.
🌕 You have boundless energy. You have just completed day 3 challenges and you are three steps ahead on your way to greatness. Now do some exercises for your brain and for your muscle.
## 💻 Day 3: Exercises
### Exercises: Level 1
1. Declare firstName, lastName, country, city, age, isMarried, year variable and assign value to it and use the typeof operator to check different data types.
1. Declare firstName, lastName, country, city, age, isMarried, year variable and assign values to it. Use the typeof operator to check different data types.
2. Check if type of '10' is equal to 10
3. Check if parseInt('9.8') is equal to 10
4. Boolean value is either true or false.
1. Write three JavaScript statement which provide truthy value.
2. Write three JavaScript statement which provide falsy value.
1. Write three JavaScript statements which provide truthy values.
2. Write three JavaScript statements which provide falsy values.
5. Figure out the result of the following comparison expression first without using console.log(). After you decide the result confirm it using console.log()
5. Figure out the result of the following comparison expression, first without using console.log(). After you get the result, confirm it using console.log():
1. Write a script that prompt the user to enter side a, side b, and side c of the triangle and and calculate the perimeter of triangle (perimeter = a + b + c)
2. Write a script that prompts the user to enter side a, side b, and side c of a triangle and then calculate the perimeter of the triangle (perimeter = a + b + c)
1. Get length and width using prompt and calculate an area of rectangle (area = length x width and the perimeter of rectangle (perimeter = 2 x (length + width))
1. Get radius using prompt and calculate the area of a circle (area = pi x r x r) and circumference of a circle(c = 2 x pi x r) where pi = 3.14.
1. Calculate the slope, x-intercept and y-intercept of y = 2x -2
1. Slope is (m = y2-y1/x2-x1). Find the slope between point (2, 2) and point(6,10)
1. Compare the slope of above two questions.
1. Calculate the value of y (y = x^2 + 6x + 9). Try to use different x values and figure out at what x value y is 0.
1. Writ a script that prompt a user to enters hours and rate per hour. Calculate pay of the person?
3. Get length and width using prompt and calculate an area of rectangle (area = length x width) and the perimeter of rectangle (perimeter = 2 x (length + width))
4. Get radius using prompt and calculate the area of a circle (area = pi x r x r) and circumference of a circle(c = 2 x pi x r) where pi = 3.14.
5. Calculate the slope, x-intercept and y-intercept of y = 2x -2
6. Slope is (m = y2-y1/x2-x1). Find the slope between point (2, 2) and point(6,10)
7. Compare the slopes in questions 5 and 6.
8. Calculate the value of y (y = x^2 + 6x + 9). Try to use different x values and figure out at what x value y is 0.
9. Writ a script that prompts a user to enter hours and rate per hour. Calculate pay of the person?
```sh
Enter hours: 40
Enter rate per hour: 28
Your weekly earning is 1120
Your weekly earnings are 1120
```
1. If the length of your name is greater than 7 say, your name is long else say your name is short.
1. Compare your first name length and your family name length and you should get this output.
10. If the length of your name is greater than 7, say your name is long, otherwise say your name is short.
11. Compare your first name length and your family name length. You should get this output.
Your first name, Asabeneh is longer than your family name, Yetayeh
```
1. Declare two variables _myAge_ and _yourAge_ and assign them initial values and myAge and yourAge.
12. Declare two variables _myAge_ and _yourAge_ and assign them initial values. Compare them and write the result as a message similar to the output below:
1. Using prompt get the year the user was born and if the user is 18 or above allow the user to drive if not tell the user to wait a certain amount of years.
13. Using prompt get the year the user was born. If the user is 18 or above allow the user to drive, if not tell the user to wait a certain amount of years.
You are 15. You will be allowed to drive after 3 years.
```
1. Write a script that prompt the user to enter number of years. Calculate the number of seconds a person can live. Assume someone lives just hundred years
14. Write a script that prompts the user to enter number of years. Calculate the number of seconds a person can live. Assume someone lives just hundred years:
```sh
Enter number of yours you live: 100
You lived 3153600000 seconds.
```
1. Create a human readable time format using the Date time object
15. Create a human readable time format using the Date time object
1. YYY-MM-DD HH:mm
2. DD-MM-YYYY HH:mm
3. DD/MM/YYY HH:mm
### Exercises: Level 3
1. Create a human readable time format using the Date time object. The hour and the minute should be all time two digits(7 hours should be 07 and 5 minutes should be 05)
1. YYY-MM-DD HH:mm eg. 20120-01-02 07:05
1. Create a human readable time format using the Date time object. The hours and the minutes output should be all the time two digits long (7 hours should be 07 and 5 minutes should be 05)
Pawel Kiczko
5 years ago