diff --git a/.gitignore b/.gitignore
index c206125d3..e8317f901 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,4 +1,6 @@
 draft.md
 playground
 /playground
-.DS_Store
\ No newline at end of file
+.DS_Store
+test.js
+day3.md
\ No newline at end of file
diff --git a/images/comparison_operators.png b/images/comparison_operators.png
new file mode 100644
index 000000000..26ccb9130
Binary files /dev/null and b/images/comparison_operators.png differ
diff --git a/images/string_indexes.png b/images/string_indexes.png
new file mode 100644
index 000000000..cc2f6389c
Binary files /dev/null and b/images/string_indexes.png differ
diff --git a/readMe.md b/readMe.md
index 26fb5dc11..30f4d14d3 100644
--- a/readMe.md
+++ b/readMe.md
@@ -32,7 +32,18 @@
   - [Checking Data types](#checking-data-types)
 - [Comments](#comments)
 - [Variables](#variables)
-- [💻 Day 1: Exercises](#-day-1-exercises)
+- [💻 Day 1: Exercises](#%f0%9f%92%bb-day-1-exercises)
+- [📔 Day 2](#%f0%9f%93%94-day-2)
+- [Data types](#data-types)
+- [Numbers](#numbers)
+  - [Declaring number data types](#declaring-number-data-types)
+  - [Math Object](#math-object)
+- [Strings](#strings)
+  - [String Concatenation](#string-concatenation)
+    - [Concatenating using addition operator](#concatenating-using-addition-operator)
+    - [Template Literals(Template Strings)](#template-literalstemplate-strings)
+  - [String Methods](#string-methods)
+- [💻 Day 2: Exercises](#%f0%9f%92%bb-day-2-exercises)
 
 
 
@@ -312,8 +323,8 @@ console.log('Hello, World!')
 
       <script src ="./helloworld.js"></script>
       <script src="./introduction.js"></script>
-    </body
-    </html
+    </body>
+  </html
 ```
 Your main.js file should be below all other scripts. Watch out your exercise needs to understand this line.
 ![Multiple Script](./images/multiple_script.png)
@@ -437,14 +448,20 @@ Invalid variable:
   1_num
   num_#_1
 ```
+Let's declare variables with different data types. To declare a variable we need let or const keyword,  the name of the variable, an equal sign (assignment operator) and a value. 
+```js
+  # Syntax
+  let nameOfVariable = value  
+```
+**Examples: Variables**
 ```js
 // Declaring different variables of different data types
-let firstName = 'Asabeneh'; // first name of a person
-let lastName = 'Yetayeh'; // last name of a person
-let country = 'Finland'; // country
-let city = 'Helsinki'; // capital city
-let age = 100; // age in years
-let isMarried = true;
+let firstName = 'Asabeneh' // first name of a person
+let lastName = 'Yetayeh' // last name of a person
+let country = 'Finland' // country
+let city = 'Helsinki' // capital city
+let age = 100 // age in years
+let isMarried = true
 console.log(firstName, lastName, country, city, age, isMarried); //Asabeneh, Yetayeh, Finland, Helsinki, 100, True
 
 // Declaring variables with number values
@@ -481,3 +498,554 @@ When you run the files on 01-Day folder you should get this:
    You are 30 years old.
   
    ```
+
+# 📔 Day 2
+# Data types
+In the previous section, we mentioned a little bit about data types. Data have data types. Data types describe the characteristics of data. Data types can be divided into 
+1. Primitive data types
+2. Non-primitive data types(Object References)
+
+
+Primitive data types in JavaScript includes:
+ 1. Numbers
+ 2. Strings
+ 3. Booleans
+ 4. Null
+ 5. Undefined
+
+Non-primitive data types in JavaScript includes:
+1. Objects
+2. Functions
+3. Arrays
+   
+Now, let us see what exactly mean primitive and non-primitive data types.
+*Primitive* data types are immutable(non-modifiable) data types. Once a primitive data type is created we can not modify it.
+**Example:**
+```js
+let word = 'JavaScript'
+```
+If we try to modify the string stored in variable *word* JavaScript will raise an error. Any data type under single quote, double quote or back tick is a string data type.
+```js
+word[0] = 'Y'
+```
+This expression does not change the string stored in the variable *word*. So, we can say strings are not modifiable or immutable.
+Primitive data types are compared by its values. Let us compare different data values. See the example below:
+```js
+let numOne = 3
+let numTwo = 3
+console.log(numOne == numTwo)      // true
+
+let js = 'JavaScript'
+let py = 'Python'
+console.log(js == py)             //false 
+
+let lightOn = true
+let lightOff = false
+console.log(lightOn == lightOff) // false
+```
+
+*Non-primitive* data types are modifiable or mutable. We can modify the value of non-primitive data types after it gets created. 
+Let us see by creating an array. Array is a list of data values in a square bracket. Array can contain the same or different data types. Arrays values are referenced by its index which starts at zero.
+```js
+let nums = [1, 2, 3]
+nums[0] = 10
+console.log(nums)  // [10, 2, 3]
+```
+As you can see, an array which a non-primitive data type is a mutable. Non-primitive data types can not be compared by value. Even if two non-primitive data types have the same properties and values, they are not strictly equal. 
+```js
+let nums = [1, 2, 3]
+let numbers = [1, 2, 3]
+console.log(nums == numbers)  // false
+
+let userOne = {
+name:'Asabeneh',
+role:'teaching',
+country:'Finland'
+}
+let userTwo = {
+name:'Asabeneh',
+role:'teaching',
+country:'Finland'
+}
+console.log(userOne == userTwo)
+```
+Rule of thumb, we do not compare non-primitive data types. Do not compare array, function or object. 
+Non-primitive values are referred to as reference types because they are being compared by reference instead of value. Two objects are only strictly equal if they refer to the same underlying object.
+```js
+let nums = [1, 2, 3]
+let numbers = nums
+console.log(nums == numbers)  // true
+
+let userOne = {
+name:'Asabeneh',
+role:'teaching',
+country:'Finland'
+}
+let userTwo = userOne
+console.log(userOne == userTwo)  // true
+```
+If you have hard time to understand the difference between primitive data types and non-primitive data types, you are not the only one. Calm down and just go to the next section and try to come back after some time. Now let us start the data types by number type. 
+
+# Numbers
+Numbers are integers and decimal values which can do all the arithmetic operations
+Lets' see some examples of Numbers
+
+## Declaring number data types
+
+```js
+let age = 35
+const gravity = 9.81 //we use const for non-changing values, gravitational constant in  m/s2
+let mass = 72 // mass in Kilogram
+const PI = 3.14 // pi a geometrical constant
+
+//More Examples
+const boilingPoint = 100 // temperature in oC, boiling point of water which is a constant
+const bodyTemp = 37 // oC average human body temperature, which is a constant
+console.log(age, gravity, mass, PI, boilingPoint, bodyTemp)
+```
+## Math Object
+In JavaScript the Math Object provides a lots of methods to work with numbers.
+```js
+const PI = Math.PI
+console.log(PI)                  // 3.141592653589793
+console.log(Math.round(PI))      // 3; to round values to the nearest number
+console.log(Math.round(9.81))    // 10
+console.log(Math.floor(PI))      // 3; rounding down
+console.log(Math.ceil(PI))       // 4; rounding up
+console.log(Math.min(-5, 3, 20, 4,5, 10))    // -5, returns the minimum value
+console.log(Math.max(-5, 3, 20, 4,5, 10))    // 20, returns the maximum value
+
+const randNum = Math.random() // creates random number between 0 to 0.999999
+console.log(randNum)
+// Let create random number between 0 to 10
+const num = Math.floor(Math.random () * 11) // creates random number between 0 and 10
+console.log(num)
+
+//Absolute value
+console.log(Math.abs(-10))    //10
+//Square root
+console.log(Math.sqrt(100))     // 10
+console.log(Math.sqrt(2))      //1.4142135623730951
+// Power
+console.log(Math.pow(3, 2)) // 9
+console.log(Math.E) // 2.718
+
+// Logarithm
+//Returns the natural logarithm of base E of x, Math.log(x)
+console.log(Math.log(2))    // 0.6931471805599453
+console.log(Math.log(10))   // 2.302585092994046
+
+// Trigonometry
+Math.sin(0)
+Math.sin(60)
+
+Math.cos(0)
+Math.cos(60)
+```
+
+# Strings
+
+Strings are text which are under **_single_** or **_double_** quote. To declare a string we need a variable name, assignment operator, a value under a single quote, double quote or back tick.
+Lets' see some examples of string:
+
+```js
+let space = ' ' // an empty space string
+let firstName = 'Asabeneh'
+let lastName = 'Yetayeh'
+let country = 'Finland'
+let city = 'Helsinki'
+let language = 'JavaScript'
+let job = 'teacher'
+```
+
+## String Concatenation
+Connect two or more strings together is called concatenation. 
+
+```js
+// Declaring different variables of different data types
+let space = ' '
+let firstName = 'Asabeneh'
+let lastName = 'Yetayeh'
+let country = 'Finland'
+let city = 'Helsinki'
+let language = 'JavaScript'
+let job = 'teacher'
+```
+
+```js
+let fullName = firstName + space + lastName; // concatenation, merging two string together.
+console.log(fullName);
+```
+```sh
+// out
+Asabeneh Yetayeh
+```
+We can concatenate string in different ways. 
+### Concatenating using addition operator
+Concatenating using addition operator is an old way. This way of concatenating is tedious and error prone. It is good to know, how to concatenate this way but I strongly suggest to use the second way.
+```js
+// Declaring different variables of different data types
+let space = ' '
+let firstName = 'Asabeneh'
+let lastName = 'Yetayeh'
+let country = 'Finland'
+let city = 'Helsinki'
+let language = 'JavaScript'
+let job = 'teacher'
+let age = 250
+let fullName = firstName + space + lastName
+let personInfoOne = fullName + '. I am ' + age + '. I live in ' + country; // ES5
+console.log(personInfoOne)
+```
+```sh
+Asabeneh Yetayeh. I am 250. I live in Finland
+```
+### Template Literals(Template Strings)
+To create a template string we use back two back ticks. We can inject data as expression inside a template string. To inject data we enclose the expression with curly bracket({}) followed by $ sign. See the syntax blow.
+```js
+//Syntax
+`String literal text`
+`String literal text ${expression}`
+```
+**Example: 1**
+
+```js
+console.log(`The sum of 2 and 3 is 5`)
+let a = 2
+let b = 3
+console.log(`The sum of ${a} and ${b} is ${a + b}`)
+```
+**Example:2**
+```js
+let firstName = 'Asabeneh'
+let lastName = 'Yetayeh'
+let country = 'Finland'
+let city = 'Helsinki'
+let language = 'JavaScript'
+let job = 'teacher'
+let age = 250
+let fullName = firstName + ' ' + lastName
+
+let personInfoTwo = `I am ${fullName}. I am ${age}. I live in ${country}.` //ES6 - String interpolation method
+let personInfoThree = `I am ${fullName}. I live in ${city}, ${country}. I am a ${job}. I teach ${language}.`
+console.log(personInfoTwo)
+console.log(personInfoThree)
+```
+```sh
+I am Asabeneh Yetayeh. I am 250. I live in Finland.
+I am Asabeneh Yetayeh. I live in Helsinki, Finland. I am a teacher. I teach JavaScript.
+```
+Using string template or string interpolation method we can add expression which could be a value or some operations(comparison, arithmetic operations, ternary operation)
+```js
+let a = 2
+let b = 3
+console.log(`${a} is greater than ${b}: ${a > b}`)
+```
+```sh
+2 is greater than 3: false
+```
+## String Methods
+Everything in JavaScript is an object. String is a primitive data type that means we can not modify once it is created. String object has many string methods. There many string methods which can help us to work with strings.
+
+1. *length*: The string *length* method returns the number of characters in a string included empty space.
+  **Example:**
+   ```js
+   let js = 'JavaScript'
+   console.log(js.length)        // 10
+   let firstName = 'Asabeneh'
+   console.log(firstName.length) // 8
+   ```
+2. *Accessing characters in a string*: We can access each characters in a string using its index. In programming counting starts from 0. The first index of the string is zero and the last index is one minus the length of the string
+   
+  ![Accessing sting by index](./images/string_indexes.png)
+Let us access the first character in 'JavaScript' string.
+```js
+let string = 'JavaScript'
+let firstLetter = string[0]
+console.log(firstLetter) // J
+let secondLetter = string[1] // a
+let thirdLetter = string[2]
+let lastLetter = string[9] 
+console.log(lastLetter) // t
+let lastIndex = string.length - 1
+console.log(lastIndex)  // 9
+console.log(string[lastIndex]) // t
+
+```
+3. *toUpperCase()*: this method changes the string to uppercase letters.
+```js
+let string = 'JavaScript'
+console.log(string.toUpperCase())      // JAVASCRIPT
+let firstName = 'Asabeneh'
+console.log(firstName.toUpperCase())  // ASABENEH
+let country = 'Finland'
+console.log(country.toUpperCase())    // FINLAND
+
+```
+
+4. *toLowerCase()*: this method changes the string to lowercase letters.
+```js
+let string = 'JavasCript'
+console.log(string.toLowerCase())     // javascript
+let firstName = 'Asabeneh'
+console.log(firstName.toLowerCase())  // asabeneh
+let country = 'Finland'
+console.log(country.toLowerCase())   // finland
+
+```
+5. *substr()*: It takes two arguments,the starting index and number of characters to slice.
+```js
+let string = 'JavaScript'
+console.log(string.substr(4,6)     // Script
+let country = 'Finland'
+console.log(country.substr(3, 4))   // land
+
+```
+6. *substring()*: It takes two arguments,the starting index and the stopping index but it doesn't include the stopping index.
+
+```js
+let string = 'JavaScript'
+console.log(string.substring(0,4)     // Java
+console.log(string.substring(4,10)     // Script
+console.log(string.substring(4)     // Script
+let country = 'Finland'
+console.log(country.substring(0, 3))   // Fin
+console.log(country.substring(3, 7))   // land
+console.log(country.substring(3))   // land
+
+```
+7. *split(): The split method splits a string at a specified place.
+
+```js
+let string = '30 Days Of JavaScipt'
+console.log(string.split())     // ["30 Days Of JavaScript"]
+console.log(string.split(' '))  // ["30", "Days", "Of", "JavaScript"]
+let firstName = 'Asabeneh'
+console.log(firstName.split())  // ["Asabeneh"]
+console.log(firstName.split(''))  // ["A", "s", "a", "b", "e", "n", "e", "h"]
+let countries = 'Finland, Sweden, Norway, Denmark, and Iceland'
+console.log(countries.split(',')) // ["Finland", " Sweden", " Norway", " Denmark", " and Iceland"]
+console.log(countries.split(', '))   //  ["Finland", "Sweden", "Norway", "Denmark", "and Iceland"]
+
+```
+8. *trim()*: Removes trailing space in the beginning or the end of a string.
+
+```js
+let string = '   30 Days Of JavaScript   '
+console.log(string)     // 
+console.log(string.trim(' '))  // 
+let firstName = ' Asabeneh '
+console.log(firstName)
+console.log(firstName.trim())  // 
+```
+```sh
+   30 Days Of JavasCript   
+30 Days Of JavasCript
+  Asabeneh 
+Asabeneh
+```
+9. *includes()*: It takes a substring argument and it check if substring argument exists in the string. *includes()* returns a boolean. It checks if a substring exist in a string and it returns true if it exists and false if it doesn't exist. 
+
+```js
+let string = '30 Days Of JavaScript'
+console.log(string.includes('Days'))     // true
+console.log(string.includes('days'))     // false
+console.log(string.includes('Script'))     // true
+console.log(string.includes('script'))     // false
+console.log(string.includes('java'))     // false
+console.log(string.includes('Java'))     // true
+
+let country = 'Finland'
+console.log(country.includes('fin')) // false
+console.log(country.includes('Fin')) // true
+console.log(country.includes('land')) // true
+console.log(country.includes('Land')) // false
+
+```
+10. *replace()*: takes to parameter the old substring and new substring.
+
+```js
+string.replace(oldsubstring, newsubstring)
+```
+```js
+let string = '30 Days Of JavaScript'
+console.log(string.replace('JavaScript', 'Python')) // 30 Days Of Python
+let country = 'Finland'
+console.log(country.replace('Fin', 'Noman')) Nomanland
+```
+11. *charAt()*: Takes index and it returns the value at that index
+```js
+string.charAt(index)
+```
+```js
+let string = '30 Days Of JavaScript'
+console.log(string.charAt(0)) // 3
+let lastIndex = string.length - 1
+console.log(string.charAt(lastIndex)) // t
+
+```
+12. *charCodeAt()*: Takes index and it returns char code(ASCII number) of the value at that index
+```js
+string.charCodeAt(index)
+```
+```js
+let string = '30 Days Of JavaScript'
+console.log(string.charCodeAt(3)) // D ASCII number is 51
+let lastIndex = string.length - 1
+console.log(string.charCodeAt(lastIndex)) // t ASCII is 116
+
+```
+13. *indexOf()*: Takes takes a substring and if the substring exists in a string it returns the first position of the substring if does not exist it returns -1
+```js
+string.indexOf(substring)
+```
+```js
+let string = '30 Days Of JavaScript'
+console.log(string.indexOf('D'))          // 3
+console.log(string.indexOf('Days'))       // 3
+console.log(string.indexOf('days'))       // -1
+console.log(string.indexOf('a'))          // 4
+console.log(string.indexOf('JavaScript')) // 11
+console.log(string.indexOf('Script'))     //15
+console.log(string.indexOf('script'))     // -1
+
+```
+14. *lastIndexOf()*: Takes takes a substring and if the substring exists in a string it returns the last position of the substring if it does not exist it returns -1
+```js
+string.charCodeAt(index)
+```
+```js
+let string = 'I love JavaScript. If you do not love JavaScript what else can you love.'
+console.log(string.lastIndexOf('love'))       // 67
+console.log(string.lastIndexOf('you'))        // 63
+console.log(string.lastIndexOf('JavaScript')) // 38
+
+```
+
+15.  *concat()*: it takes many substrings and creates concatenation.
+```js
+string.concate(substring, substring, substring)
+```
+```js
+let string = '30'
+console.log(string.concat("Days", "Of", "JavaScript")) // 30DaysOfJavaScript
+let country = 'Fin'
+console.log(country.concat("land")) // Finland
+
+```
+
+16.   *startsWith*: it takes a substring as an argument and it checks if the string starts with that specified substring. It returns a boolean(true or false).
+```js
+string.startsWith(substring)
+```
+```js
+let string = 'Love is the best to in this world'
+console.log(string.startsWith('Love')) // true
+console.log(string.startsWith('love')) // false
+console.log(string.startsWith('world')) // false
+
+let country = 'Finland'
+console.log(country.startsWith('Fin')) // true
+console.log(country.startsWith('fin')) // false
+console.log(country.startsWith('land')) //  false
+
+```
+17.   *endsWith*: it takes a substring as an argument and it checks if the string starts with that specified substring. It returns a boolean(true or false).
+```js
+string.endsWith(substring)
+```
+```js
+let string = 'Love is the best to in this world'
+console.log(string.endsWith('world')) // true
+console.log(string.endsWith('love')) // false
+console.log(string.endsWith('in this world')) // true
+
+let country = 'Finland'
+console.log(country.endsWith('land')) // true
+console.log(country.endsWith('fin')) // false
+console.log(country.endsWith('Fin')) //  false
+
+```
+18.    *search*: it takes a substring as an argument and it returns the index of the first match.
+```js
+string.serch(substring)
+```
+```js
+let string = 'I love JavaScript. If you do not love JavaScript what else can you love.'
+console.log(string.search('love')) // 2
+
+```
+1.     *match*: it takes a substring or regular expression pattern as an argument and it returns an array if there is match if not it returns null. Let us see how a regular expresson pattern looks like. It starts with / sign and ends with / sign. 
+  ```js
+  let string = 'love'
+  let patternOne = /love/ // with out any flag
+  let patternTwo = /love/gi // g-means to search in the whole text, i - case insensitive
+
+  ```
+```js
+string.match(substring)
+```
+```js
+let string = 'I love JavaScript. If you do not love JavaScript what else can you love.'
+console.log(string.match('love')) //
+/*
+output
+
+["love", index: 2, input: "I love JavaScript. If you do not love JavaScript what else can you love.", groups: undefined]
+*/
+let pattern = /love/gi
+console.log(string.match(pattern)) // ["love", "love", "love"]
+
+```
+Let us extract numbers from text using regular expression. This is not regular expression section, no panic.
+```js
+
+let txt = 'In 2019, I run 30 Days of Pyhton. Now, in 2020 I super exited to start this challenge'
+let regEx = /\d+/ // d with escape character means d not a normal d instead acts a digit
+// + means one or more digit numbers, 
+// if there is g after that it means global, search everywhere.
+console.log(text.match(regEx)) // ["2", "0", "1", "9", "3", "0", "2", "0", "2", "0"]
+console.log(text.match(/\d+/g)) // ["2019", "30", "2020"]
+```
+
+
+# 💻  Day 2: Exercises
+
+1. Declare a variable name challenge and assign it to an initial value **'30 Days Of JavaScript'**.
+2. Print the string on the browser console using __console.log()__
+3. Print the __length__ of the string on the browser console using _console.log()_
+4. Change all the string to capital letters using __toUpperCase()__ method
+5. Change all the string to lowercase letters using __toLowerCase()__ method
+6. Cut(slice) out the first word of the string using __substr()__ or __substring()__ method
+7. Slice out the phrase *Days Of JavaScript* from *30 Days Of JavaScript*.
+8. Use __substr__ to slice out the phase __because because because__ in the following sentence:__'You cannot end a sentence with because because because is a conjunction'__
+9. Check if the string contains a word __Script__ using __includes()__ method
+10. Split the __string__ into __array__ using __split()__ method
+11. Split the string 30 Days Of JavaScript at the space using __split()__ method
+12. 'Facebook, Google, Microsoft, Apple, IBM, Oracle, Amazon' __split__ the string at the comma and change it to an array.
+13. Change 30 Days Of JavaScript to Microsoft Academy using __replace()__ method.
+14. What is character at index 15 in '30 Days Of JavaScript' string use __charAt()__ method.
+15. What is the character code of J in '30 Days Of JavaScript' string using __charCodeAt()__
+16. Use __indexOf__ to determine the position of the first occurrence of a in 30 Days Of JavaScript
+17. Use __lastIndexOf__ to determine the position of the last occurrence of a in 30 Days Of JavaScript.
+18. Use __indexOf__ to find the position of the first occurrence of the word __because__ in the following sentence:__'You cannot end a sentence with because because because is a conjunction'__
+19. Use __lastIndexOf__ to find the position of the first occurrence of the word __because__ in the following sentence:__'You cannot end a sentence with because because because is a conjunction'__
+20. Use __search__ to find the position of the first occurrence of the word __because__ in the following sentence:__'You cannot end a sentence with because because because is a conjunction'__
+21. Use __trim()__ to remove if there is trailing whitespace at the beginning and the end of a string.E.g ' 30 Days Of JavaScript '.
+22. Use __startsWith()__ method with the string *30 Days Of JavaScript* make the result true
+23. Use __endsWith()__ method with the string *30 Days Of JavaScript* make the result true
+24. Use __match()__ method to find all the a’s in 30 Days Of JavaScript
+25. Use __match()__ to count the number all because's in the following sentence:__'You cannot end a sentence with because because because is a conjunction'__
+26. Use __concat()__ and merge '30 Days of' and 'JavaScript' to a single string, '30 Days Of JavaScript'
+27. Use __repeat()__ method to print 30 Days Of JavaScript 2 times
+28. Love is the best thing in this world. Some found their love and some are still looking for their love. Count the number of word love in this sentence.
+29. Calculate the total annual income of the person by extract the numbers from the following text. 'He earns 5000 euro from salary per month, 10000 euro annual bonus, 15000 euro online courses per month.'
+30. Clean the following text(hint, use replace and regular express)
+```js
+    sentence = '%I $am@% a %tea@cher%, &and& I lo%#ve %tea@ching%;. There $is nothing; &as& mo@re rewarding as educa@ting &and& @emp%o@wering peo@ple. ;I found tea@ching m%o@re interesting tha@n any other %jo@bs. %Do@es thi%s mo@tivate yo@u to be a tea@cher!?'
+```
+
+
+
+
+