• Number EX: 1 2 3
• String EX: "anytext"
  
• Boolean EX: true or false
  
• Null EX: value null represents the intentional absence of a value
• Undefined
• Symbol

• Object
• Array

Math is a built in function so we can use anywhere in our program

• Math.random (Returns a random decimal)
  
• Math.floor (Round down to nearest integer)
  
• Math.ceil (Round up to nearest integer)
  
• Math.round (Round to nearest integer)
  EXAMPLE:
• Math.round(4.15) would output 4
  
• Math.round(4.80) would output 5

3.1 There are three ways to declare a string param:

• ""
• ''
• ``

3.2 The common string functions:

• length
• replace
• indexOf
• search
• upperCase
• lowerCase
• trim
• split

There are two ways:
"string 1" + "string 2"
and
abc ${var1} abc ${var2} abc

parseInt("123") prints 123
parseInt("30 years old") prints 30
parseInt("Jean is 30 years old") prints NaN

var
let
const

=
+=
-=
*=
Full list at:
https://www.w3schools.com/js/js_assignment.asp

Falsey : false 0 '' "" `` NaN null undefined

The rest of variables are Truthy : 1, 2, true, 1, "a", {}, numbers other than 0, new Date();. 8.1. Type safe comparison operators: Strictly equal: === Strictly unequal: !==

what is the difference between ! and !! ?
! : returns the inverse of original value
EX: let i = 2
i != 1
returns true
!! : returns the original value of a boolean
what is the difference between == and === ?
== : does the type conversion of the operand before comparison (loose equality)
=== : operator compares the value as well as the data types of the operand (strict equality).

Note: Unlike == operator, === doesn't do type conversion.

Comparing string and number: the string is converted into a number before the comparison.
Comparing boolean and number (0 or 1): it treats 0 as false and 1 as true.
Comparing two objects: the operator will check if both refer to the same object. If yes then the == operator will return true and != will return false, otherwise == will return false and != will return true.
Comparing null and undefined: the == operator will return true and != operator will return false.

&& operator requires both left and right values to be true to return true.
|| Operator requires only one of the values to be true to return true, and only false || false will return false.

.toString() returns a string. .pop() removes and returns the last item of the array .push(item1, ..., itemN) Adds one or more items to the end
.reverse() reverses the order in which the array is organized .shift() removes and returns the first item of the array .unshift(item) adds an item to the front of the array

toString() join() pop() push() shift() unshift() splice() concat() slice() includes() map reduce filter()

spread is a definition rest -> next lesson

const array1 = ['a', 'b', 'c']; const array2 = ['d', 'e', 'f']; const array3 = array1.concat(array2);

console.log(array3); // expected output: Array ["a", "b", "c" , "d", "e", "f"]

// in ES6 we have a powerful method to concat two arrays we call it spread

const array1 = ['a', 'b', 'c']; const array2 = ['d', 'e', 'f']; const array3 = array1.concat(array2); //old way const array3 = [...array1, ...array2] //new way

if
else

const age = 12

let allowed

if (age === 32) { allowed = 'trung' } else if (age == 30) { allowed = 'Jean' } else { allowed = 'Other' }

console.log(allowed)

//// //Ternary operator const age = 12 const allowed = age > 18 ? 'yes' : 'no' console.log(allowed)

we can convert a simple if else function to ternary with complex if else function we can not do that

If using many else if, then use switch swith are the same with if else function

const food = 'apple';

switch(food) { case 'pear': console.log('I like pears'); break; case 'apple': console.log('I like apples'); break; case 'orange': console.log('mmm... citrus'); break; default: // it is not required

console.log('idk what that is');

// compiler and interpreter // the javascript compiler will help us compile the source code

let n = 0 while (n < 5) { // false the while stops

console.log(${n} is ${n % 2 ? 'odd' : 'even'}) n++ // n = 5 } line 1: 0 is odd line 2: 1 is even line 3: 2 is odd line 5: 4 is even

1%2 => 1 2%2 => 0 3%2 => 1 4%2 => 0

3%3 0 58%9 4 58 = 9*6 + 4

for (let i = 0; i < 10; i++) { console.log(i); // do more stuff } element

array of objects const wizards = [ {name: "Harry Potter", house: "Gryffindor"}, // first element {name: "Lord Voldomort", house: "Slytherin"}, // second element {name: "Cedric Diggory", house: "Hufflepuff"}, {name: "Luna Lovegood", house: "Ravenclaw"},
{name: "Albus Dumbledor", house: "Gryffindor"}, {name: "Merlin", house: "Slytherin"}, {name: "Pomona Sprout", house: "Hufflepuff"}, {name: "Gilderoy Lockheart", house: "Ravenclaw"}, {name: "Ron Weasley", house: "Gryffindor"}, {name: "Severus Snape", house: "Slytherin"}, {name: "Nymphadora Tonks", house: "Hufflepuff"}, {name: "Padma Patil", house: "Ravenclaw"}, {name: "Hermoine Granger", house: "Gryffindor"} ]

wizards[0] wizards[1]

array objects

functions fnName(params) {

}

// ES6 const fnName = (params) => {

}

f(-2) => -4 f(-1) => -2 f(0) => 0 f(1) => 2 f(2) => 4

Here you have to write a function that the name is f

const fnName = (num) => { let i = -2 while (i < 10){ i++ console.log(i) } } fnName(-2) => result: -4

f only a function name so you can use f1 f2 fAbc ... instead

the name of function, variable avoid keywords like const, let, function, string ...

const movie1 = 'Saving Private Ryan'; const year1 = 1998; console.log(${movie1} was released in ${year1});

const movie2 = 'Interstellar'; const year2 = 2014; console.log(${movie2} was released in ${year2});

const movie3 = 'Jason Bourne'; const year3 = 2016; console.log(${movie3} was released in ${year3});

const theMovieData = (movie, year) => { console.log(The movie ${movie} was release in year ${year}) } theMovieData(movie1,year1) legendary definition

"abcd"[1] -> b index 0: a index 1: b nth 1 : a nth 2 : b nth 3 : c

function myFunction(a, n) { return a[n - 1] }

str.slice(str.length,-3)

// get last 3 letters str.slice(str.length -3, str.length) str.slice(str.length -3) str.slice(-3)

"abcdefg" ef

fucntion myFunction(str){ return str.slice(-3, -1) return str.slice(4, 5) }

if (a.includes()) {

}

b + a ${a}${b}

ternary operator function myFunction(a, b) { return a.indexOf(b) === -1 ? a + b : b + a }

1%2 1 2%2 0 3%2 1 4%2 0

8 is even because 8%2 is 0

function myFunction(a) { let isEven = true

if (Math.abs(a%2) == 1) { // absolute isEven = false }

return isEven }

-5 % 2 ? absolute -1 is 1

-3 % 2 => -1 1

Absolute of -1 is 1

Absolute -4 is 4 the result of absolute is always more than 0

function myFunction(a) { return a % 2 === 0 } jschanllanger 10 score get 20 scores in https://leetcode.com to become a senior frontend developer you have to get 100 scores: Javascript 30 scores Reac tJS 25 scores css 5 scores , experience(50 scores)

10 scores

you dont recommend to learn about React, untill i have this understood properly. depth understanding

I have to understand JS in depth before i learn React

I am going to Argentina on August 12, I arrive to Argentina the 13th , then i come back from Argentina on August 30, Arrive to NY on August 31st

stage

we will keep in touch, we will make it work, if we cannot speak every day, at least 1 hour or 30 minutes for important questions i may have.

in Argentina I need to repair things in my grandpas house and i need to visit family

ill do the best i can to make it work.

depends on your time

yes but also yours. You know Im busy from 9am to 6pm in VietName at other time I can teach you

how about tomorrow ? 7am(monday) here 8pm(sunday) there ?