The catch block take a parameter. It is common to pass e, err or error as a parameter to the catch block. This parameter is an object and it has name and message keys. Lets use the name and message.
| 24 | [Mini Project: Solar System](./24_Day_Project_solar_system/24_day_project_solar_system.md) |
| 25 | [Mini Project: World Countries Data Visulalization 1](./25_Day_World_countries_data_visualization_1/25_day_world_countries_data_visualization_1.md) |
| 26 | [Mini Project: World Countries Data Visulalization 2](./26_Day_World_countries_data_visualization_2/26_day_world_countries_data_visualization_2.md) |
| 24 | [Mini Project: Solar System](./24_Day_Project_solar_system/24_day_project_solar_system.md) |
| 25 | [Mini Project: World Countries Data Visulalization 1](./25_Day_World_countries_data_visualization_1/25_day_world_countries_data_visualization_1.md) |
| 26 | [Mini Project: World Countries Data Visulalization 2](./26_Day_World_countries_data_visualization_2/26_day_world_countries_data_visualization_2.md) |
- [Introduction to Data types](#introduction-to-data-types)
- [Number](#number)
- [String](#string)
- [Numbers](#numbers)
- [Strings](#strings)
- [Booleans](#booleans)
- [Undefined](#undefined)
- [Null](#null)
@ -109,12 +109,12 @@
## Introduction
**Congratulations** for deciding to participate in 30 days of JavaScript programming challenge. In this challenge you will learn everything you need to be a JavaScript programmer, and in general, the whole concept of programming. In the end of the challenge you will get a 30DaysOfJavaScript programming challenge completion certificate. In case you need help or if you would like to help others you may join the [telegram group](https://t.me/ThirtyDaysOfJavaScript).
**Congratulations** on deciding to participate in 30 days of JavaScript programming challenge. In this challenge you will learn everything you need to be a JavaScript programmer, and in general, the whole concept of programming. In the end of the challenge you will get a 30DaysOfJavaScript programming challenge completion certificate. In case you need help or if you would like to help others you may join the [telegram group](https://t.me/ThirtyDaysOfJavaScript).
**A 30DaysOfJavaScript** challenge is a guide for both beginners and advanced JavaScript developers. Welcome to JavaScript. I enjoy using and teaching JavaScript and I hope you will do so too. JavaScript is the language of the web.
**A 30DaysOfJavaScript** challenge is a guide for both beginners and advanced JavaScript developers. Welcome to JavaScript.JavaScript is the language of the web. I enjoy using and teaching JavaScript and I hope you will do so too.
In this step by step tutorial, you will learn JavaScript, the most popular programming language in the history of mankind.
You use JavaScript **_to add interactivity to websites, to develop mobile apps, desktop applications, games_** and nowadays JavaScript can be used for **_machine learning_** and **_AI_**.
In this step by step JavaScript challenge, you will learn JavaScript, the most popular programming language in the history of mankind.
JavaScript is used**_to add interactivity to websites, to develop mobile apps, desktop applications, games_** and nowadays JavaScript can be used for **_machine learning_** and **_AI_**.
**_JavaScript (JS)_** has increased in popularity in recent years and has been the leading
programming language for six consecutive years and is the most used programming language on
Github.
@ -124,14 +124,14 @@ Github.
No prior knowledge of programming is required to follow this challenge. You need only:
1. Motivation
2. Computer
2. A computer
3. Internet
4. Browser
5. Code Editor
4. A browser
5. A code editor
## Setup
I believe you have the motivation and a strong desire to be a developer, computer and Internet. If you have those, then you have everything to get started.
I believe you have the motivation and a strong desire to be a developer, a computer and Internet. If you have those, then you have everything to get started.
### Install Node.js
@ -141,7 +141,7 @@ You may not need node.js right now but you may need it for later. Install [node.
After downloading double click and install
We can check if node is installed on our local machine by opening our device terminal or command prompt.
After you open the Google Chrome console, try to explore the marked buttons. We will spend most of the time on the Console part. The Console is the place where your JavaScript code goes. The Google Console V8 engine changes your JavaScript code to machine code.
After you open the Google Chrome console, try to explore the marked buttons. We will spend most of the time on the Console. The Console is the place where your JavaScript code goes. The Google Console V8 engine changes your JavaScript code to machine code.
Let us write a JavaScript code on the Google Chrome console:
@ -207,7 +207,7 @@ console.log('Hello, World!')
##### Console.log with Multiple Arguments
The console.log(param1, param2, param3), can take multiple arguments.
The **conole.log()** function can take multiple parameters separated by comma. The syntax looks like as follows:**console.log(param1, param2, param3)**
As you can see from the snippet code above, *console.log()* can take multiple arguments.
As you can see from the snippet code above, _console.log()_ can take multiple arguments.
Congratulations! You wrote your first JavaScript code using *console.log()*.
Congratulations! You wrote your first JavaScript code using _console.log()_.
##### Comment
##### Comments
We add comments to our code. Comments are very important to make code more readable and to leave remarks in our code. JavaScript does not execute the comment part of our code. Any text line starting with // in JavaScript is a comment or anything enclosed like this /* */ is a comment.
We add comments to our code. Comments are very important to make code more readable and to leave remarks in our code. JavaScript does not execute the comment part of our code.In JavaScript, any text line starting with // in JavaScript is a comment, and anything enclosed like this /\* \*/ is also a comment.
**Example: Single Line Comment**
// This is the first comment
// This is the first comment
// This is the second comment
// I am a single line comment
// I am a single line comment
**Example: Multiline Comment**
/*
This is a multiline comment
Multiline comments can take multiple lines
JavaScript is the language of the web
*/
/_
This is a multiline comment
Multiline comments can take multiple lines
JavaScript is the language of the web
_/
##### Syntax
Programming languages are similar to human languages. English language or any other language uses words, phrases, sentences,compound sentences and other more to convey a meaningful message. The English meaning of syntax is *the arrangement of words and phrases to create well-formed sentences in a language*. The technical definition of syntax is *the structure of statements in a computer language.* Programing languages have syntax. JavaScript is a programming language and like other programming languages it has its own syntax. If we do not write a syntax that JavaScript understands, it will raise different types of errors. We will explore different kinds of JavaScript errors later. For now, let us see syntax errors.
Programming languages are similar to human languages. English or many other language uses words, phrases, sentences,compound sentences and other more to convey a meaningful message. The English meaning of syntax is _the arrangement of words and phrases to create well-formed sentences in a language_. The technical definition of syntax is _the structure of statements in a computer language._ Programing languages have syntax. JavaScript is a programming language and like other programming languages it has its own syntax. If we do not write a syntax that JavaScript understands, it will raise different types of errors. We will explore different kinds of JavaScript errors later. For now, let us see syntax errors.
I made a deliberate mistake. As a result, the console raises a syntax error. Actually, the syntax is very informative. It informs what type of mistake we made. By reading the error feedback guideline, we can correct the syntax and fix the problem. The process of identifying and removing errors from a program is called debugging. Let us fix the errors:
I made a deliberate mistake. As a result, the console raises syntax errors. Actually, the syntax is very informative. It informs what type of mistake was made. By reading the error feedback guideline, we can correct the syntax and fix the problem. The process of identifying and removing errors from a program is called debugging. Let us fix the errors:
```js
console.log("Hello, World!")
console.log('Hello, World!')
console.log('Hello, World!')
```
So far, we saw how to display text using a *console.log()*. If we are printing text or string using *console.log()*, the text has to be under the single quote, double quote, or a backtick quote.
So far, we saw how to display text using the _console.log()_. If we are printing text or string using _console.log()_, the text has to be inside the single quotes, double quotes, or a backtick quotes.
**Example:**
```js
console.log("Hello, World!")
console.log('Hello, World!')
console.log('Hello, World!')
console.log(`Hello, World!`)
```
#### Arithmetics
Now, let us practice more writing JavaScript codes using *console.log()* on google chrome console for number data types.
Now, let us practice more writing JavaScript codes using _console.log()_ on google chrome console for number data types.
In addition to the text, we can also do mathematical calculations using JavaScript. Let us do the following simple calculations.
The console can directly take arguments without the **_console.log()_** function. However, it is included in this introduction because most of this challenge would be taking place in a text editor where the usage of the function would be mandatory. You can play around directly with instructions on the console.
We can write our codes on the browser console, but it won't do for bigger projects. In a real working environment, developers use different code editors to write their codes. In this 30 days JavaScript challenge, we will use Visual Studio Code.
We can write our codes on the browser console, but it won't do for bigger projects. In a real working environment, developers use different code editors to write their codes. In this 30 days JavaScript challenge, we will be using Visual Studio Code.
#### Installing Visual Studio Code
Visual studio code is a very popular open-source text editor. I would recommend to [download Visual Studio Code](https://code.visualstudio.com/), but if you are in favor of other editors, feel free to follow with what you have.
Visual studio code is a very popular open-source text editor. I would recommend to [download Visual Studio Code](https://code.visualstudio.com/), but if you are in favor of other editors, feel free to follow with what you have.
@ -310,6 +311,7 @@ Open the Visual Studio Code by double-clicking its icon. When you open it, you w
## Adding JavaScript to a Web Page
JavaScript can be added to a web page in three different ways:
- **_Inline script_**
- **_Internal script_**
- **_External script_**
@ -319,21 +321,21 @@ The following sections show different ways of adding JavaScript code to your web
### Inline Script
Create a folder on your desktop and call it 30DaysOfJS or in any location and create an **_index.html_** file in the project folder. Then paste the following code and open it in a browser, for example [Chrome](https://www.google.com/chrome/).
Create a project folder on your desktop or in any location, name it 30DaysOfJS and create an **_index.html_** file in the project folder. Then paste the following code and open it in a browser, for example [Chrome](https://www.google.com/chrome/).
```html
<!DOCTYPE html>
<html>
<head>
<title>30DaysOfScript:Inline Script</title>
</head>
<body>
<buttononclick="alert('Welcome to 30DaysOfJavaScript!')">Click Me</button>
</body>
</html>
<html>
<head>
<title>30DaysOfScript:Inline Script</title>
</head>
<body>
<buttononclick="alert('Welcome to 30DaysOfJavaScript!')">Click Me</button>
</body>
</html>
```
Now, you wrote your first inline script. We can create a pop up alert message using the built-in *alert()* function.
Now, you just wrote your first inline script. We can create a pop up alert message using the _alert()_ built-in function.
### Internal Script
@ -342,33 +344,32 @@ First, let us write on the head part of the page.
```html
<!DOCTYPE html>
<html>
<head>
<title>30DaysOfScript:Internal Script</title>
<script>
console.log("Welcome to 30DaysOfJavaScript")
</script>
</head>
<body>
</body>
</html>
<html>
<head>
<title>30DaysOfScript:Internal Script</title>
<script>
console.log('Welcome to 30DaysOfJavaScript')
</script>
</head>
<body></body>
</html>
```
This is how we write an internal script most of the time. Writing the JavaScript code in the body section is the most preferred option. Open the browser console to see the output from the console.log()
```html
<!DOCTYPE html>
<html>
<head>
<title>30DaysOfScript:Internal Script</title>
</head>
<body>
<buttononclick="alert('Welcome to 30DaysOfJavaScript!');">Click Me</button>
<script>
console.log("Welcome to 30DaysOfJavaScript");
</script>
</body>
</html>
<html>
<head>
<title>30DaysOfScript:Internal Script</title>
</head>
<body>
<buttononclick="alert('Welcome to 30DaysOfJavaScript!');">Click Me</button>
<script>
console.log('Welcome to 30DaysOfJavaScript')
</script>
</body>
</html>
```
Open the browser console to see the output from the console.log()
@ -378,7 +379,7 @@ Open the browser console to see the output from the console.log()
### External Script
Similar to the internal script, the external script link can be on the header or body, but it is preferred to put it in the body.
First, we should create an external JavaScript file with .js extension. All files ending with .js extension are JavaScript files. Create a file introduction.js inside your project directory and write the following code and link this .js file at the bottom of the body.
First, we should create an external JavaScript file with .js extension. All files ending with .js extension. All files ending with .js extension are JavaScript files. Create a file named introduction.js inside your project directory and write the following code and link this .js file at the bottom of the body.
```js
console.log('Welcome to 30DaysOfJavaScript')
@ -388,37 +389,36 @@ External scripts in the _head_:
```html
<!DOCTYPE html>
<html>
<head>
<title>30DaysOfJavaScript:External script</title>
<scriptsrc="introduction.js"></script>
</head>
<body>
</body>
</html>
<html>
<head>
<title>30DaysOfJavaScript:External script</title>
<scriptsrc="introduction.js"></script>
</head>
<body></body>
</html>
```
External scripts in the _body_:
```html
<!DOCTYPE html>
<html>
<head>
<title>30DaysOfJavaScript:External script</title>
</head>
<body>
//it could be in the header or in the body
// Here is the recommended place to put the external script
<scriptsrc="introduction.js"></script>
</body>
</html>
<html>
<head>
<title>30DaysOfJavaScript:External script</title>
</head>
<body>
//it could be in the header or in the body // Here is the recommended place
to put the external script
<scriptsrc="introduction.js"></script>
</body>
</html>
```
Open the browser console to see the output from the console.log()
Open the browser console to see the output of the console.log()
### Multiple External Scripts
We can link multiple external JavaScript files to a web page.
We can also link multiple external JavaScript files to a web page.
Create a helloworld.js file inside the 30DaysOfJS folder and write the following code.
```js
@ -427,19 +427,18 @@ console.log('Hello, World!')
```html
<!DOCTYPE html>
<html>
<head>
<title>Multiple External Scripts</title>
</head>
<body>
<scriptsrc ="./helloworld.js"></script>
<scriptsrc="./introduction.js"></script>
</body>
</html>
<html>
<head>
<title>Multiple External Scripts</title>
</head>
<body>
<scriptsrc="./helloworld.js"></script>
<scriptsrc="./introduction.js"></script>
</body>
</html>
```
*Your main.js file should be below all other scripts*. It is very important to remember this.
_Your main.js file should be below all other scripts_. It is very important to remember this.
@ -447,28 +446,27 @@ console.log('Hello, World!')
In JavaScript and also other programming languages, there are different kinds of data types. The following are JavaScript primitive data types:_String, Number, Boolean, undefined, Null_, and _Symbol_.
### Number
### Numbers
- Integer: Integer (negative, zero and positive) numbers
Example:
... -3, -2, -1, 0, 1, 2, 3 ...
- Float: Decimal number
Example
... -3.5, -2.25, -1.0, 0.0, 1.1, 2.2, 3.5 ...
- Integers: Integer (negative, zero and positive) numbers
Example:
... -3, -2, -1, 0, 1, 2, 3 ...
- Float-point numbers: Decimal number
Example
... -3.5, -2.25, -1.0, 0.0, 1.1, 2.2, 3.5 ...
### String
### Strings
A collection of one or more characters under a single quote, double quote, or backtick quote.
A collection of one or more characters between two single quotes, double quotes, or backticks.
**Example:**
```js
'Asabeneh'
'Finland'
'JavaScript is a beautiful programming language'
"I love teaching"
'I hope you are enjoying the first day'
`We can also create a string using a backtick`
'A string could be just as small as one character as big as many pages'
'I love teaching'
'I hope you are enjoying the first day'`We can also create a string using a backtick`
;('A string could be just as small as one character as big as many pages')
```
### Booleans
@ -480,8 +478,8 @@ A boolean data type is either a true or false value.
**Example:**
```js
true // if the light on ,the value is true
false // if the light off, the value is false
true // if the light on ,the value is true
false // if the light off, the value is false
```
### Undefined
@ -489,8 +487,8 @@ A boolean data type is either a true or false value.
In JavaScript, if we don't assign a value to a variable, the value is undefined. In addition to that, if a function is not returning anything, it returns undefined.
```js
let firstName;
console.log(firstName); //not defined, because it is not assigned to a value yet
let firstName
console.log(firstName) //not defined, because it is not assigned to a value yet
```
### Null
@ -507,15 +505,15 @@ To check the data type of a certain variable, we use the **typeof** operator. Se
```js
console.log(typeof 'Asabeneh') // string
console.log(typeof 5) // number
console.log(typeof true) // boolean
console.log(typeof null) // object type
console.log(typeof undefined) // undefined
console.log(typeof 5) // number
console.log(typeof true) // boolean
console.log(typeof null) // object type
console.log(typeof undefined) // undefined
```
## Comments Again
Reminding, that commenting in JavaScript is similar to other programming languages. Comments are important in making your make code more readable.
Remember that commenting in JavaScript is similar to other programming languages. Comments are important in making your code more readable.
There are two ways of commenting:
- _Single line commenting_
@ -540,44 +538,44 @@ Multiline commenting:
## Variables
Variables are _containers_ of data. Variables used to _store_ data in a memory location. When a variable is declared, a memory location is reserved. When a variable is assigned to a value (data), the memory space will be filled with that data. To declare a variable, we use _var_, _let_, or _const_ keywords. We will talk more about var, let, and const in detail in other sections (scope). For now, the above explanation is enough.
Variables are _containers_ of data. Variables are used to _store_ data in a memory location. When a variable is declared, a memory location is reserved. When a variable is assigned to a value (data), the memory space will be filled with that data. To declare a variable, we use _var_, _let_, or _const_ keywords.
For a variable that changes at a different time, we use _let_. If the data does not change at all, we use _const_. For example, PI, country name, gravity do no change, and we can use *const*. We will not use var in this challenge and I don't recommend you to use it. It is error prone way of declaring variable it has lots of leak.
For a variable that changes at a different time, we use _let_. If the data does not change at all, we use _const_. For example, PI, country name, gravity do no change, and we can use _const_. We will not use var in this challenge and I don't recommend you to use it. It is error prone way of declaring variable it has lots of leak. We will talk more about var, let, and const in detail in other sections (scope). For now, the above explanation is enough.
A valid JavaScript
A valid JavaScript variable name must follow the following rules:
- A JavaScript variable name should not begin with a number.
- A JavaScript variable name should not begin with a number.
- A JavaScript variable name does not allow special characters except dollar sign and underscore.
- A JavaScript variable name follows a camelCase convention.
- A JavaScript variable name should not have space between words.
The following are valid examples of JavaScript variables.
Valid variables in JavaScript:
The following are examples of valid JavaScript variables.
```js
firstName
lastName
country
city
capitalCity
age
isMarried
first_name
last_name
is_married
capital_city
num1
num_1
_num_1
$num1
year2020
year_2020
```
camelCase or the first way of declaring is conventional in JavaScript. In this material, we will use camelCase variables.
Invalid variables:
firstName
lastName
country
city
capitalCity
age
isMarried
first_name
last_name
is_married
capital_city
num1
num_1
_num_1
$num1
year2020
year_2020
```
The first and second variables on the list follows the camelCase convention of declaring in JavaScrip. In this material, we will use camelCase variables.
Example of invalid variables:
```sh
first-name
@ -585,14 +583,14 @@ Invalid variables:
num_#_1
```
Let us declare variables with different data types. To declare a variable, we need to use let or const keyword before the variable name. Following the variable name, we write an equal sign (assignment operator), and a value.
Let us declare variables with different data types. To declare a variable, we need to use *let* or *const* keyword before the variable name. Following the variable name, we write an equal sign (assignment operator), and a value(assigned data).
```js
// Syntax
let nameOfVariable = value
// Syntax
let nameOfVariable = value
```
**Examples: Variables**
**Examples of declared variables**
```js
// Declaring different variables of different data types
@ -612,10 +610,10 @@ Asabeneh Yetayeh Finland Helsinki 100 True
```js
// Declaring variables with number values
let age = 100 // age in years
const gravity = 9.81 // earth gravity in m/s2
const boilingPoint = 100 // water boiling point, temperature in oC
const PI = 3.14 // geometrical constant
let age = 100 // age in years
const gravity = 9.81 // earth gravity in m/s2
const boilingPoint = 100 // water boiling point, temperature in oC
// Variables can also be declaring in one line separated by comma
let name = 'Asabeneh', // name of a person
job = 'teacher',
live = 'Finland';
console.log(name, job, live);
live = 'Finland'
console.log(name, job, live)
```
```sh
Asabeneh teacher Finland
```
When you run the files on 01-Day folder you should get this:
When you run _index.html_ file in the 01-Day folder you should get this:
🌕 You are amazing! You have just completed day 1 challenge and you are on your way to greatness. Now do some exercises for your brain and for your muscle.
🌕 You are amazing! You have just completed day 1 challenge and you are on your way to greatness. Now do some exercises for your brain and muscle.
# 💻 Day 1: Exercises
1. Write a single line comment which says, _comments can make code readable_
2. Write another single comment which says, *Welcome to 30DaysOfJavaScript*
2. Write another single comment which says, _Welcome to 30DaysOfJavaScript_
3. Write a multiline comment which says, _comments can make code readable, easy to reuse_
_and informative_
4. Create a variable.js file and declare variables and assign string, boolean, undefined and null data types
5. Create datatypes.js file and use the JavaScript ***typeof*** operator to check different data types. Check the data type of each variable
5. Create datatypes.js file and use the JavaScript **_typeof_** operator to check different data types. Check the data type of each variable
6. Declare four variables without assigning values
7. Declare four variables with assigning values
7. Declare four variables with assigned values
8. Declare variables to store your first name, last name, marital status, country and age in multiple lines
9. Declare variables to store your first name, last name, marital status, country and age in a single line
10. Declare two variables _myAge_ and _yourAge_ and assign them initial values and log to the browser console.
Asabeneh
4 years ago