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Background Context

JavaScript is used for many things. Here, you will use JavaScript for 2 reasons:

  • Scripting (same as we did with Python)
  • Web front-end

For the moment, and for learning all basic concepts of this language, we will do some scripting. After, we will make our AirBnB project dynamic by using Javascript and JQuery.

Please run

Resources

Read or watch:

Learning Objectives

At the end of this project, you are expected to be able to explain to anyone, without the help of Google:

General

  • Why JavaScript programming is amazing
  • How to run a JavaScript script
  • How to create variables and constants
  • What are differences between var, const and let
  • What are all the data types available in JavaScript
  • How to use the if, if ... else statements
  • How to use comments
  • How to affect values to variables
  • How to use while and for loops
  • How to use break and continue statements
  • What is a function and how do you use functions
  • What does a function that does not use any return statement return
  • Scope of variables
  • What are the arithmetic operators and how to use them
  • How to manipulate dictionary
  • How to import a file

Requirements

General

  • Allowed editors: vi, vim, emacs
  • All your files will be interpreted on Ubuntu 20.04 LTS using node (version 14.x)
  • All your files should end with a new line
  • The first line of all your files should be exactly #!/usr/bin/node
  • A README.md file, at the root of the folder of the project, is mandatory
  • Your code should be semistandard compliant (version 16.x.x). Rules of Standard + semicolons on top. Also as reference: AirBnB style
  • All your files must be executable
  • The length of your files will be tested using wc

More Info

Install Node 14

$ curl -sL https://deb.nodesource.com/setup_14.x | sudo -E bash -
$ sudo apt-get install -y nodejs

Install semi-standard

Documentation

$ sudo npm install semistandard --global

Quiz questions

Question #0

Does Javascript have String as a native datatype?

  • No

  • Yes

Question #1

Does Javascript have Dictionary as a native datatype?

  • No

  • Yes

Tips:

Everything is Object and Object type in Javascript is powerful.

Question #2

Does Javascript have Array as a native datatype?

  • No

  • Yes

Question #3

Does Javascript have Set as a native datatype?

  • No

  • Yes

Question #4

What does let mean? (please check all true answers)

  • It’s the keyword to define a variable that can be re-assign during the execution

  • It’s the keyword to define a variable in the local scope

  • It’s the keyword to define a global variable

  • It’s the keyword to define a constant variable

  • It’s the keyword to define a variable with optionally initializing it to a value

Question #5

What does const mean? (please check all true answers)

  • It’s the keyword to define a variable that can be re-assign during the execution

  • It’s the keyword to define a variable in the local scope

  • It’s the keyword to define a global variable

  • It’s the keyword to define a constant variable

  • It’s the keyword to define a variable with optionally initializing it to a value

Tasks

0. First constant, first print

Write a script that prints “JavaScript is amazing”:

  • You must create a constant variable called myVar with the value “JavaScript is amazing”
  • You must use console.log(...) to print all output
  • You are not allowed to use var
guillaume@ubuntu:~/0x12$ ./0-javascript_is_amazing.js
JavaScript is amazing
guillaume@ubuntu:~/0x12$
guillaume@ubuntu:~/0x12$ semistandard ./0-javascript_is_amazing.js
guillaume@ubuntu:~/0x12$

Repo:

  • GitHub repository: alx-higher_level_programming
  • Directory: 0x12-javascript-warm_up
  • File: 0-javascript_is_amazing.js

1. 3 languages

Write a script that prints 3 lines:

  • The first line: “C is fun”
  • The second line: “Python is cool”
  • The third line: “JavaScript is amazing”
  • You must use console.log(...) to print all output
  • You are not allowed to use var
guillaume@ubuntu:~/0x12$ ./1-multi_languages.js
C is fun
Python is cool
JavaScript is amazing
guillaume@ubuntu:~/0x12$

Repo:

  • GitHub repository: alx-higher_level_programming
  • Directory: 0x12-javascript-warm_up
  • File: 1-multi_languages.js

2. Arguments

Write a script that prints a message depending of the number of arguments passed:

  • If no arguments are passed to the script, print “No argument”
  • If only one argument is passed to the script, print “Argument found”
  • Otherwise, print “Arguments found”
  • You must use console.log(...) to print all output
  • You are not allowed to use var

Reference: process.argv

guillaume@ubuntu:~/0x12$ ./2-arguments.js
No argument
guillaume@ubuntu:~/0x12$ ./2-arguments.js Best
Argument found
guillaume@ubuntu:~/0x12$ ./2-arguments.js Best School
Arguments found
guillaume@ubuntu:~/0x12$

Repo:

  • GitHub repository: alx-higher_level_programming
  • Directory: 0x12-javascript-warm_up
  • File: 2-arguments.js

3. Value of my argument

Write a script that prints the first argument passed to it:

  • If no arguments are passed to the script, print “No argument”
  • You must use console.log(...) to print all output
  • You are not allowed to use var
  • You are not allowed to use length
guillaume@ubuntu:~/0x12$ ./3-value_argument.js
No argument
guillaume@ubuntu:~/0x12$ ./3-value_argument.js School
School
guillaume@ubuntu:~/0x12$

Repo:

  • GitHub repository: alx-higher_level_programming
  • Directory: 0x12-javascript-warm_up
  • File: 3-value_argument.js

4. Create a sentence

Write a script that prints two arguments passed to it, in the following format: “ is ”

  • You must use console.log(...) to print all output
  • You are not allowed to use var
guillaume@ubuntu:~/0x12$ ./4-concat.js c cool
c is cool
guillaume@ubuntu:~/0x12$ ./4-concat.js c
c is undefined
guillaume@ubuntu:~/0x12$ ./4-concat.js
undefined is undefined
guillaume@ubuntu:~/0x12$

Repo:

  • GitHub repository: alx-higher_level_programming
  • Directory: 0x12-javascript-warm_up
  • File: 4-concat.js

5. An Integer

Write a script that prints My number: <first argument converted in integer> if the first argument can be converted to an integer:

  • If the argument can’t be converted to an integer, print “Not a number”
  • You must use console.log(...) to print all output
  • You are not allowed to use var
  • You are not allowed to use try/catch
guillaume@ubuntu:~/0x12$ ./5-to_integer.js
Not a number
guillaume@ubuntu:~/0x12$ ./5-to_integer.js 89
My number: 89
guillaume@ubuntu:~/0x12$ ./5-to_integer.js "89"
My number: 89
guillaume@ubuntu:~/0x12$ ./5-to_integer.js 89.89
My number: 89
guillaume@ubuntu:~/0x12$ ./5-to_integer.js School
Not a number
guillaume@ubuntu:~/0x12$

Repo:

  • GitHub repository: alx-higher_level_programming
  • Directory: 0x12-javascript-warm_up
  • File: 5-to_integer.js

6. Loop to languages

Write a script that prints 3 lines: (like 1-multi_languages.js) but by using an array of string and a loop

  • The first line: “C is fun”
  • The second line: “Python is cool”
  • The third line: “JavaScript is amazing”
  • You must use console.log(...) to print all output
  • You are not allowed to use var
  • You are not allowed to use any if/else statement
  • You can use only one console.log
  • You must use a loop (while, for, etc.)
guillaume@ubuntu:~/0x12$ ./6-multi_languages_loop.js
C is fun
Python is cool
JavaScript is amazing
guillaume@ubuntu:~/0x12$

Repo:

  • GitHub repository: alx-higher_level_programming
  • Directory: 0x12-javascript-warm_up
  • File: 6-multi_languages_loop.js

7. I love C

Write a script that prints x times “C is fun”

  • Where x is the first argument of the script
  • If the first argument can’t be converted to an integer, print “Missing number of occurrences”
  • You must use console.log(...) to print all output
  • You are not allowed to use var
  • You can use only two console.log
  • You must use a loop (while, for, etc.)
guillaume@ubuntu:~/0x12$ ./7-multi_c.js 2
C is fun
C is fun
guillaume@ubuntu:~/0x12$ ./7-multi_c.js 5
C is fun
C is fun
C is fun
C is fun
C is fun
guillaume@ubuntu:~/0x12$ ./7-multi_c.js
Missing number of occurrences
guillaume@ubuntu:~/0x12$ ./7-multi_c.js -3
guillaume@ubuntu:~/0x12$

Repo:

  • GitHub repository: alx-higher_level_programming
  • Directory: 0x12-javascript-warm_up
  • File: 7-multi_c.js

8. Square

Write a script that prints a square

  • The first argument is the size of the square
  • If the first argument can’t be converted to an integer, print “Missing size”
  • You must use the character X to print the square
  • You must use console.log(...) to print all output
  • You are not allowed to use var
  • You must use a loop (while, for, etc.)
guillaume@ubuntu:~/0x12$ ./8-square.js
Missing size
guillaume@ubuntu:~/0x12$ ./8-square.js School
Missing size
guillaume@ubuntu:~/0x12$ ./8-square.js 2
XX
XX
guillaume@ubuntu:~/0x12$ ./8-square.js 6
XXXXXX
XXXXXX
XXXXXX
XXXXXX
XXXXXX
XXXXXX
guillaume@ubuntu:~/0x12$ ./8-square.js -3
guillaume@ubuntu:~/0x12$

Repo:

  • GitHub repository: alx-higher_level_programming
  • Directory: 0x12-javascript-warm_up
  • File: 8-square.js

9. Add

Write a script that prints the addition of 2 integers

  • The first argument is the first integer
  • The second argument is the second integer
  • You have to define a function with this prototype: function add(a, b)
  • You must use console.log(...) to print all output
  • You are not allowed to use var
guillaume@ubuntu:~/0x12$ ./9-add.js
NaN
guillaume@ubuntu:~/0x12$ ./9-add.js 1
NaN
guillaume@ubuntu:~/0x12$ ./9-add.js 1 7
8
guillaume@ubuntu:~/0x12$ ./9-add.js 13 89
102
guillaume@ubuntu:~/0x12$

Repo:

  • GitHub repository: alx-higher_level_programming
  • Directory: 0x12-javascript-warm_up
  • File: 9-add.js

10. Factorial

Write a script that computes and prints a factorial

  • The first argument is integer (argument can be cast as integer) used for computing the factorial
  • Factorial of NaN is 1
  • You must do it recursively
  • You must use a function
  • You must use console.log(...) to print all output
  • You are not allowed to use var
guillaume@ubuntu:~/0x12$ ./10-factorial.js
1
guillaume@ubuntu:~/0x12$ ./10-factorial.js 3
6
guillaume@ubuntu:~/0x12$ ./10-factorial.js 89
1.6507955160908452e+136
guillaume@ubuntu:~/0x12$ ./10-factorial.js 333
Infinity
guillaume@ubuntu:~/0x12$

Repo:

  • GitHub repository: alx-higher_level_programming
  • Directory: 0x12-javascript-warm_up
  • File: 10-factorial.js

11. Second biggest!

Write a script that searches the second biggest integer in the list of arguments.

  • You can assume all arguments can be converted to integer
  • If no argument passed, print 0
  • If the number of arguments is 1, print 0
  • You must use console.log(...) to print all output
  • You are not allowed to use var
guillaume@ubuntu:~/0x12$ ./11-second_biggest.js
0
guillaume@ubuntu:~/0x12$ ./11-second_biggest.js 1
0
guillaume@ubuntu:~/0x12$ ./11-second_biggest.js 4 2 5 3 0 -3
4
guillaume@ubuntu:~/0x12$

Repo:

  • GitHub repository: alx-higher_level_programming
  • Directory: 0x12-javascript-warm_up
  • File: 11-second_biggest.js

12. Object

Update this script to replace the value 12 with 89:

  • You are not allowed to use var
guillaume@ubuntu:~/0x12$ cat 12-object.js
#!/usr/bin/node
const myObject = {
  type: 'object',
  value: 12
};
console.log(myObject);
/*
YOUR CODE HERE
*/
console.log(myObject);

guillaume@ubuntu:~/0x12$ ./12-object.js
{ type: 'object', value: 12 }
{ type: 'object', value: 89 }
guillaume@ubuntu:~/0x12$

Repo:

  • GitHub repository: alx-higher_level_programming
  • Directory: 0x12-javascript-warm_up
  • File: 12-object.js

13. Add file

Write a function that returns the addition of 2 integers.

  • The function must be visible from outside
  • The name of the function must be add
  • You are not allowed to use var

Tip

guillaume@ubuntu:~/0x12$ cat 13-main.js
#!/usr/bin/node
const add = require('./13-add').add;
console.log(add(3, 5));
guillaume@ubuntu:~/0x12$ ./13-main.js
8
guillaume@ubuntu:~/0x12

Repo:

  • GitHub repository: alx-higher_level_programming
  • Directory: 0x12-javascript-warm_up
  • File: 13-add.js

14. Const or not const

Write a file that modifies the value of myVar to 333

guillaume@ubuntu:~/0x12$ cat 100-main.js
#!/usr/bin/node
myVar = 89;
require('./100-let_me_const')
console.log(myVar);
guillaume@ubuntu:~/0x12$ ./100-main.js
333
guillaume@ubuntu:~/0x12$

const

Do you get it? Talk about it!

Hint: Scope

This exercise doesn’t pass semistandard so don’t worry about it.

Repo:

  • GitHub repository: alx-higher_level_programming
  • Directory: 0x12-javascript-warm_up
  • File: 100-let_me_const.js

15. Call me Moby

Write a function that executes x times a function.

  • The function must be visible from outside
  • Prototype: function (x, theFunction)
  • You are not allowed to use var
guillaume@ubuntu:~/0x12$ cat 101-main.js
#!/usr/bin/node
const callMeMoby = require('./101-call_me_moby').callMeMoby;
callMeMoby(3, function () {
  console.log('C is fun');
});
guillaume@ubuntu:~/0x12$ ./101-main.js
C is fun
C is fun
C is fun
guillaume@ubuntu:~/0x12$

Repo:

  • GitHub repository: alx-higher_level_programming
  • Directory: 0x12-javascript-warm_up
  • File: 101-call_me_moby.js

16. Add me maybe

Write a function that increments and calls a function.

  • The function must be visible from outside
  • Prototype: function (number, theFunction)
  • You are not allowed to use var
guillaume@ubuntu:~/0x12$ cat 102-main.js
#!/usr/bin/node
const addMeMaybe = require('./102-add_me_maybe').addMeMaybe;
addMeMaybe(4, function (nb) {
  console.log('New value: ' + nb);
});
guillaume@ubuntu:~/0x12$ ./102-main.js
New value: 5
guillaume@ubuntu:~/0x12$

Repo:

  • GitHub repository: alx-higher_level_programming
  • Directory: 0x12-javascript-warm_up
  • File: 102-add_me_maybe.js

17. Increment object

Update this script by adding a new function incr that increments the integer value.

  • You are not allowed to use var
guillaume@ubuntu:~/0x12$ cat 103-object_fct.js
#!/usr/bin/node
const myObject = {
  type: 'object',
  value: 12
};
console.log(myObject);
/*
YOUR CODE HERE
*/
myObject.incr();
console.log(myObject);
myObject.incr();
console.log(myObject);
myObject.incr();
console.log(myObject);

guillaume@ubuntu:~/0x12$ ./103-object_fct.js
{ type: 'object', value: 12 }
{ type: 'object', value: 13, incr: [Function] }
{ type: 'object', value: 14, incr: [Function] }
{ type: 'object', value: 15, incr: [Function] }
guillaume@ubuntu:~/0x12$

Repo:

  • GitHub repository: alx-higher_level_programming
  • Directory: 0x12-javascript-warm_up
  • File: 103-object_fct.js