diff --git a/exercise-ansver-key/day1_introdiction.js b/exercise-ansver-key/01_day_introdiction.js
similarity index 64%
rename from exercise-ansver-key/day1_introdiction.js
rename to exercise-ansver-key/01_day_introdiction.js
index 09f5ea0..851003d 100644
--- a/exercise-ansver-key/day1_introdiction.js
+++ b/exercise-ansver-key/01_day_introdiction.js
@@ -1,17 +1,21 @@
 //---------------------------day1_level_1 1.exercise ------------------------\\
+// Write a single line comment which says, comments can make code readable
 
 // comments can make code readable
 
 //---------------------------day1_level_1 2.exercise-------------------------\\
+// Write another single comment which says, Welcome to 30DaysOfJavaScript
 
 //Welcome to 30DaysOfJavaScript
 
 //---------------------------day1_level_1 3.exercise-------------------------\\
+// Write a multiline comment which says, comments can make code readable, easy to reuse and informative
 
 /*        comments can make code readable,
            easy to reuse and informative  */
 
 //---------------------------day1_level_1 4.exercise-------------------------\\
+// Create a variable.js file and declare variables and assign string, boolean, undefined and null data types
 
 //variable.js
 let string = 'nevzat'
@@ -21,6 +25,7 @@ let nulll = null
 let any;     //undefined
 
 //---------------------------day1_level_1 5.exercise-------------------------\\
+// Create datatypes.js file and use the JavaScript typeof operator to check different data types. Check the data type of each variable
 
 //type.js
 console.log(typeof (string) )
@@ -30,6 +35,7 @@ console.log(typeof (nulll))
 console.log(typeof (any))
 
 //---------------------------day1_level_1 6.exercise-------------------------\\
+// Declare four variables without assigning values
 
     let variable1;
     let variable2;
@@ -37,6 +43,7 @@ console.log(typeof (any))
     let variable4;
 
 //---------------------------day1_level_1 7. exercise------------------------\\
+// Declare four variables with assigned values
 
 variable1 = "nevzat"
 variable2 = "ATALAY"
@@ -44,6 +51,7 @@ variable3 =  true;
 variable4 = 25;
 
 //---------------------------day1_level_1 8.exercise-------------------------\\
+// Declare variables to store your first name, last name, marital status, country and age in multiple lines
 
 let firstName = "nevzat"
 let lastName = "atalay"
@@ -51,12 +59,14 @@ let old = 25
 let isMarried = true
 
 //---------------------------day1_level_1 9.exercise-------------------------\\
+// Declare variables to store your first name, last name, marital status, country and age in a single line
 
 let name = "nevzat",surName="atalay",age = 25, married = true
 
 //---------------------------day1_level_1 10.exercise------------------------\\
+// Declare two variables myAge and yourAge and assign them initial values and log to the browser console.
 
-myAge= 25
+let myAge= 25
 let yourAge = 22
 
 console.log("I am " + " " +  myAge + " " + "years old.")
diff --git a/exercise-ansver-key/02_day_datatype.js b/exercise-ansver-key/02_day_datatype.js
new file mode 100644
index 0000000..4fe6580
--- /dev/null
+++ b/exercise-ansver-key/02_day_datatype.js
@@ -0,0 +1,337 @@
+//----------------------------day2_level1 1.exercise-------------------------\\
+// Declare a variable named challenge and assign it to an initial 
+value '30 Days Of JavaScript'.
+
+let challenge = '30 days of javascript'
+
+//----------------------------day2_level1 2.exercise-------------------------\\
+// Print the string on the browser console using console.log()
+
+challenge = '30 days of javascript'
+console.log(challenge)
+
+//----------------------------day2_level1 3.exercise-------------------------\\
+// Print the length of the string on the browser console using console.log()
+
+challenge = '30 days of javascript'
+console.log(challenge.length)
+
+//----------------------------day2_level1 4.exercise-------------------------\\
+// Change all the string characters to capital letters using toUpperCase()
+method
+
+challenge = '30 days of javascript'
+console.log(challenge.toUpperCase())
+
+//----------------------------day2_level1 5.exercise-------------------------\\
+// Change all the string characters to lowercase letters using toLowerCase()
+method
+
+challenge = '30 days of javascript'
+console.log(challenge.toLowerCase())
+
+
+//----------------------------day2_level1 6.exercise-------------------------\\
+// Cut (slice) out the first word of the string using substr() or substring()
+method
+
+challenge = '30 days of javascript'
+console.log(challenge.substring(3, 5))
+
+
+//----------------------------day2_level1 7.exercise-------------------------\\
+// Slice out the phrase Days Of JavaScript from 30 Days Of JavaScript.
+
+challenge = '30 days of javascript'
+let newChallenge = challenge.slice(3,10)
+console.log(newChallenge)
+
+//----------------------------day2_level1 8.exercise-------------------------\\
+// Check if the string contains a word Script using includes() method
+
+challenge = '30 days of javascript'
+console.log(challenge.includes('script'))
+
+//----------------------------day2_level1 9.exercise-------------------------\\
+// Split the string into an array using split() method
+
+challenge = '30 days of javascript'
+console.log(challenge.split(""))
+
+//----------------------------day2_level1 10.exercise------------------------\\
+// Split the string 30 Days Of JavaScript at the space using split() method
+
+challenge = '30 days of javascript'
+console.log(challenge.split(" "))
+
+//----------------------------day2_level1 11.exercise------------------------\\
+// 'Facebook, Google, Microsoft, Apple, IBM, Oracle, Amazon' split the string
+at the comma and change it to an array.
+
+let companies = 'Facebook, Google, Microsoft, Apple, IBM, Oracle,Amazon'
+console.log(companies.split(`,`))
+
+//----------------------------day2_level1 12.exercise------------------------\\
+// Change 30 Days Of JavaScript to 30 Days Of Python using replace() method.
+
+challenge = "30 days of javascript"
+console.log(challenge.replace("javascript","phyton"))
+
+//----------------------------day2_level1 13.exercise------------------------\\
+// What is character at index 15 in '30 Days Of JavaScript' string? 
+Use charAt() method.
+
+challenge = "30 days of javascript"
+console.log(challenge.charAt(15))
+
+//----------------------------day2_level1 14.exercise------------------------\\
+// What is the character code of J in '30 Days Of JavaScript' string using 
+charCodeAt()
+
+challenge = "30 days of javascript"
+console.log(challenge.charCodeAt("j"))
+
+//----------------------------day2_level1 15.exercise------------------------\\
+// Use indexOf to determine the position of the first occurrence 
+of a in 30 Days Of JavaScript
+
+challenge = "30 days of javascript"
+console.log(challenge.indexOf("a"))
+
+//----------------------------day2_level1 16.exercise------------------------\\
+// Use lastIndexOf to determine the position of the last occurrence of a in
+30 Days Of JavaScript.
+
+challenge = "30 days of javascript"
+console.log(challenge.lastIndexOf("a"))
+
+//----------------------------day2_level1 17.exercise------------------------\\
+// 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'
+
+let sentence = "You cannot end a sentence with because because is a conjunction."
+console.log(challenge.indexOf("because"))
+
+//----------------------------day2_level1 18.exercise------------------------\\
+// Use lastIndexOf to find the position of the last occurrence of the word 
+because in the following sentence:'You cannot end a sentence with because
+because because is a conjunction'
+
+sentence = "You cannot end a sentence with because because is a conjunction."
+console.log(challenge.lastIndexOf("because"))
+
+//----------------------------day2_level1 19.exercise------------------------\\
+// 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'
+
+sentence = "You cannot end a sentence with because because is a conjunction."
+console.log(challenge.search("because"))
+
+//----------------------------day2_level1 20.exercise------------------------\\
+// Use trim() to remove any trailing whitespace at the beginning and the end 
+of a string.E.g ' 30 Days Of JavaScript '.
+
+challenge = "30 Days Of JavaScript       "
+console.log(challenge.trim())
+
+//----------------------------day2_level1 21.exercise------------------------\\
+// Use startsWith() method with the string 30 Days Of JavaScript and make the 
+result true
+
+challenge = "30 Days Of JavaScript"
+console.log(challenge.startsWith(30))
+
+//----------------------------day2_level1 22.exercise------------------------\\
+// Use endsWith() method with the string 30 Days Of JavaScript and make the 
+result true
+
+challenge = "30 Days Of JavaScript"
+console.log(challenge.endsWith("JavaScript"))
+
+//----------------------------day2_level1 23.exercise------------------------\\
+// Use match() method to find all the a’s in 30 Days Of JavaScript
+
+challenge = "30 Days Of JavaScript"
+console.log(challenge.match("a"))
+
+//----------------------------day2_level1 24.exercise------------------------\\
+// Use concat() and merge '30 Days of' and 'JavaScript' to a single string,
+'30 Days Of JavaScript'
+
+let stringOne = "30 Days Of "
+let stringTwo = "JavaScript"
+console.log(stringOne.concat(stringTwo))
+
+//----------------------------day2_level1 25.exercise------------------------\\
+// Use repeat() method to print 30 Days Of JavaScript 2 times
+
+challenge = "30 Days Of JavaScript"
+console.log(challenge.repeat(2))
+
+
+//____________________________starting_exercise_level2_______________________\\
+
+
+//----------------------------day2_level2 1.exercise-------------------------\\
+// Using console.log() print out the following statement:
+
+console.log("The quote 'There is no exercise better for the heart than reaching
+down and lifting people up.' by John Holmes teaches us to help one another.")
+
+//----------------------------day2_level2 2.exercise-------------------------\\
+// Using console.log() print out the following quote by Mother Teresa:
+
+console.log("Love is not patronizing and charity isn't about pity, it is about
+love. Charity and love are the same -- with charity you give love, so don't 
+just give money but reach out your hand instead.")
+
+//----------------------------day2_level2 3.exercise-------------------------\\
+// Using console.log() print out the following quote by Mother Teresa:
+
+let number = "10"
+console.log(number===10)
+
+let number1 = 10
+console.log(number1===10)
+
+//----------------------------day2_level2 4.exercise-------------------------\\
+// Check if parseFloat('9.8') is equal to 10 if not make it exactly 
+equal with 10.
+
+let parseNumber =parseFloat(9.8)
+console.log(number===10)
+
+let ceilNumber = Math.ceil(parseFloat(9.8))
+console.log(number1===10)
+
+//----------------------------day2_level2 5.exercise-------------------------\\
+// Check if 'on' is found in both python and jargon
+
+let string = "phyton"
+let string1 ="jargon"
+console.log(string.includes("on") && string1.includes("on"))
+
+//----------------------------day2_level2 6.exercise-------------------------\\
+// I hope this course is not full of jargon. Check if jargon is in the sentence.
+
+let str = "I hope this course is not full of jargon."
+console.log(str.includes("jargon"))
+
+//----------------------------day2_level2 7.exercise-------------------------\\
+// Generate a random number between 0 and 100 inclusively.
+
+console.log(parseInt(Math.random()*101))
+
+//----------------------------day2_level2 8.exercise-------------------------\\
+// Generate a random number between 50 and 100 inclusively.
+
+console.log(parseInt(Math.random()*51+50))
+
+//----------------------------day2_level2 9.exercise-------------------------\\
+// Generate a random number between 0 and 255 inclusively.
+
+console.log(parseInt(Math.random()*255))
+
+//----------------------------day2_level2 10.exercise------------------------\\
+// Access the 'JavaScript' string characters using a random number.
+
+let word="javasicript"
+let n =parseInt(Math.random()*11)
+console.log(word[n])
+
+//----------------------------day2_level2 11.exercise------------------------\\
+// Use console.log() and escape characters to print the following pattern.
+
+console.log("1 1 1 1 1 \n2 1 2 4 8 \n3 1 3 9 27 \n4 1 4 16 64 \n5 1 5 25 125 ")
+
+//----------------------------day2_level2 12.exercise------------------------\\
+// Use substr to slice out the phrase because because because from the 
+following sentence:'You cannot end a sentence with because because because is
+a conjunction'
+
+let statement = "You cannot end a sentence with because because because 
+is a conjunction"
+console.log(statement.replace("because",""))
+
+
+
+//____________________________starting_exercise_level3_______________________\\
+
+
+
+//----------------------------day2_leve3 1.exercise--------------------------\\
+// '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.
+
+let strng ="Love is the best thing in this world. Some found their love and
+some are still looking for their love."
+let count = strng.match(/love/gi)||[].length
+console.log(count)
+
+//----------------------------day2_leve3 2.exercise--------------------------\\
+// Use match() to count the number of all because in the following sentence:
+'You cannot end a sentence with because because because is a conjunction'
+
+let sentence1 = "You cannot end a sentence with because because because
+is a conjunction"
+let count1 = sentence1.match(/because/gi)||[].length
+console.log(count1)
+
+//----------------------------day2_leve3 3.exercise--------------------------\\
+// Clean the following text and find the most frequent word 
+(hint, use replace and regular expressions).
+
+let messySentence = '%I $am@% a %tea@cher%, &and& I lo%#ve %te@a@ching%;.
+The@re $is no@th@ing; &as& mo@re rewarding as educa@ting &and& 
+@emp%o@weri@ng peo@ple. ;I found tea@ching m%o@re interesting tha@n
+any ot#her %jo@bs. %Do@es thi%s mo@tiv#ate yo@u to be a tea@cher!? 
+%Th#is 30#Days&OfJavaScript &is al@so $the $resu@lt of &love& of
+tea&ching';
+
+let cleanSentence = messySentence.replace(/[^a-zA-Z ]/g, " ");
+let words = cleanSentence.split(' ');
+let wordCounts = {};
+for(let i = 0; i < words.length; i++) {
+    if(words[i] !== '') {
+        wordCounts[words[i]] = (wordCounts[words[i]] || 0) + 1;
+    }
+}
+
+let maxWord = '';
+let maxCount = 0;
+for(let word in wordCounts) {
+    if(wordCounts[word] > maxCount) {
+        maxCount = wordCounts[word];
+        maxWord = word;
+    }
+}
+
+console.log(`Most frequent word is '${maxWord}' with count ${maxCount}`);
+
+//----------------------------day2_leve3 4.exercise--------------------------\\
+// Calculate the total annual income of the person by extracting the numbers
+from the following text. 'He earns 5000 euro from salary per month, 10000 euro
+annual bonus, 15000 euro online courses per month.'
+
+let text ='He earns 5000 euro from salary per month, 10000 euro annual bonus,
+15000 euro online courses per month.'
+
+let pattern =/\d+/g
+let numbers = text.match(pattern)
+numbers = numbers.map(Number);
+
+let montlySalary = numbers[0]
+let bonus = numbers[1]
+let montlyCourses = numbers[2]
+
+console.log(`Annual income is ${montlySalary*12 +
+bonus + montlyCourses *12} euro `)
+
+
+
+
+
+
+