From c028e373061f90b31d7f0fcbe9b833b0977a46d0 Mon Sep 17 00:00:00 2001
From: MD SHANAWAZ <91983494+123shanawaz@users.noreply.github.com>
Date: Fri, 14 Oct 2022 02:02:34 +0530
Subject: [PATCH] Create data_type.js

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+Data Types
+In the previous section, we mentioned a little bit about data types. Data or values have data types. Data types describe the characteristics of data. Data types can be divided into two:
+
+Primitive data types
+Non-primitive data types(Object References)
+Primitive Data Types
+Primitive data types in JavaScript include:
+
+Numbers - Integers, floats
+Strings - Any data under single quote, double quote or backtick quote
+Booleans - true or false value
+Null - empty value or no value
+Undefined - a declared variable without a value
+Symbol - A unique value that can be generated by Symbol constructor
+Non-primitive data types in JavaScript includes:
+
+Objects
+Arrays
+Now, let us see what exactly primitive and non-primitive data types mean. Primitive data types are immutable(non-modifiable) data types. Once a primitive data type is created we cannot modify it.
+
+Example:
+
+let word = 'JavaScript'
+If we try to modify the string stored in variable word, JavaScript should raise an error. Any data type under a single quote, double quote, or backtick quote is a string data type.
+
+word[0] = 'Y'
+This expression does not change the string stored in the variable word. So, we can say that strings are not modifiable or in other words immutable. Primitive data types are compared by its values. Let us compare different data values. See the example below:
+
+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
+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. An array is a list of data values in a square bracket. Arrays can contain the same or different data types. Array values are referenced by their index. In JavaScript array index starts at zero. I.e., the first element of an array is found at index zero, the second element at index one, and the third element at index two, etc.
+
+let nums = [1, 2, 3]
+nums[0] = 10
+
+console.log(nums)  // [10, 2, 3]
+As you can see, an array, which is a non-primitive data type is mutable. Non-primitive data types cannot be compared by value. Even if two non-primitive data types have the same properties and values, they are not strictly equal.
+
+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) // false
+Rule of thumb, we do not compare non-primitive data types. Do not compare arrays, functions, or objects. 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.
+
+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 a hard time understanding 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. Let's see some examples of Numbers.
+
+Declaring Number Data Types
+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.
+
+const PI = Math.PI
+
+console.log(PI)                            // 3.141592653589793
+
+// Rounding to the closest number
+// if above .5 up if less 0.5 down rounding
+
+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 us  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 with base E of x, Math.log(x)
+console.log(Math.log(2))        // 0.6931471805599453
+console.log(Math.log(10))       // 2.302585092994046
+
+// Returns the natural logarithm of 2 and 10 respectively
+console.log(Math.LN2)           // 0.6931471805599453
+console.log(Math.LN10)          // 2.302585092994046
+
+// Trigonometry
+Math.sin(0)
+Math.sin(60)
+
+Math.cos(0)
+Math.cos(60)
+Random Number Generator
+The JavaScript Math Object has a random() method number generator which generates number from 0 to 0.999999999...
+
+let randomNum = Math.random() // generates 0 to 0.999...
+Now, let us see how we can use random() method to generate a random number between 0 and 10:
+
+let randomNum = Math.random()         // generates 0 to 0.999
+let numBtnZeroAndTen = randomNum * 11
+
+console.log(numBtnZeroAndTen)         // this gives: min 0 and max 10.99
+
+let randomNumRoundToFloor = Math.floor(numBtnZeroAndTen)
+console.log(randomNumRoundToFloor)    // this gives between 0 and 10
+Strings
+Strings are texts, which are under single , double, back-tick quote. To declare a string, we need a variable name, assignment operator, a value under a single quote, double quote, or backtick quote. Let's see some examples of strings:
+
+let space = ' '           // an empty space string
+let firstName = 'Asabeneh'
+let lastName = 'Yetayeh'
+let country = 'Finland'
+let city = 'Helsinki'
+let language = 'JavaScript'
+let job = 'teacher'
+let quote = "The saying,'Seeing is Believing' is not correct in 2020."
+let quotWithBackTick = `The saying,'Seeing is Believing' is not correct in 2020.`
+String Concatenation
+Connecting two or more strings together is called concatenation. Using the strings declared in the previous String section:
+
+let fullName = firstName + space + lastName; // concatenation, merging two string together.
+console.log(fullName);
+Asabeneh Yetayeh
+We can concatenate strings in different ways.
+
+Concatenating Using Addition Operator
+Concatenating using the 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 ES6 template strings (explained later on).
+
+// 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 string addition
+
+console.log(personInfoOne)
+Asabeneh Yetayeh. I am 250. I live in Finland
+Long Literal Strings
+A string could be a single character or paragraph or a page. If the string length is too big it does not fit in one line. We can use the backslash character (\) at the end of each line to indicate that the string will continue on the next line. Example:
+
+const paragraph = "My name is Asabeneh Yetayeh. I live in Finland, Helsinki.\
+I am a teacher and I love teaching. I teach HTML, CSS, JavaScript, React, Redux, \
+Node.js, Python, Data Analysis and D3.js for anyone who is interested to learn. \
+In the end of 2019, I was thinking to expand my teaching and to reach \
+to global audience and I started a Python challenge from November 20 - December 19.\
+It was one of the most rewarding and inspiring experience.\
+Now, we are in 2020. I am enjoying preparing the 30DaysOfJavaScript challenge and \
+I hope you are enjoying too."
+
+console.log(paragraph)
+Escape Sequences in Strings
+In JavaScript and other programming languages \ followed by some characters is an escape sequence. Let's see the most common escape characters:
+
+\n: new line
+\t: Tab, means 8 spaces
+\\: Back slash
+\': Single quote (')
+\": Double quote (")
+console.log('I hope everyone is enjoying the 30 Days Of JavaScript challenge.\nDo you ?') // line break
+console.log('Days\tTopics\tExercises')
+console.log('Day 1\t3\t5')
+console.log('Day 2\t3\t5')
+console.log('Day 3\t3\t5')
+console.log('Day 4\t3\t5')
+console.log('This is a backslash  symbol (\\)') // To write a backslash
+console.log('In every programming language it starts with \"Hello, World!\"')
+console.log("In every programming language it starts with \'Hello, World!\'")
+console.log('The saying \'Seeing is Believing\' isn\'t correct in 2020')
+Output in console:
+
+I hope everyone is enjoying the 30 Days Of JavaScript challenge.
+Do you ?
+Days  Topics  Exercises
+Day 1 3 5
+Day 2 3 5
+Day 3 3 5
+Day 4 3 5
+This is a backslash  symbol (\)
+In every programming language it starts with "Hello, World!"
+In every programming language it starts with 'Hello, World!'
+The saying 'Seeing is Believing' isn't correct in 2020
+Template Literals (Template Strings)
+To create a template strings, we use two back-ticks. We can inject data as expressions inside a template string. To inject data, we enclose the expression with a curly bracket({}) preceded by a $ sign. See the syntax below.
+
+//Syntax
+`String literal text`
+`String literal text ${expression}`
+Example: 1
+
+console.log(`The sum of 2 and 3 is 5`)              // statically writing the data
+let a = 2
+let b = 3
+console.log(`The sum of ${a} and ${b} is ${a + b}`) // injecting the data dynamically
+Example:2
+
+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 ${language}.`
+console.log(personInfoTwo)
+console.log(personInfoThree)
+I am Asabeneh Yetayeh. I am 250. I live in Finland.
+I am Asabeneh Yetayeh. I live in Helsinki, Finland. I am a teacher. I teach JavaScript.
+Using a string template or string interpolation method, we can add expressions, which could be a value, or some operations (comparison, arithmetic operations, ternary operation).
+
+let a = 2
+let b = 3
+console.log(`${a} is greater than ${b}: ${a > b}`)
+2 is greater than 3: false
+String Methods
+Everything in JavaScript is an object. A string is a primitive data type that means we can not modify it once it is created. The string object has many string methods. There are different string methods that can help us to work with strings.
+
+length: The string length method returns the number of characters in a string included empty space.
+Example:
+
+let js = 'JavaScript'
+console.log(js.length)         // 10
+let firstName = 'Asabeneh'
+console.log(firstName.length)  // 8
+Accessing characters in a string: We can access each character 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 the length of the string minus one.
+Accessing sting by index
+
+Let us access different characters in 'JavaScript' string.
+
+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
+toUpperCase(): this method changes the string to uppercase letters.
+let string = 'JavaScript'
+
+console.log(string.toUpperCase())     // JAVASCRIPT
+
+let firstName = 'Asabeneh'
+
+console.log(firstName.toUpperCase())  // ASABENEH
+
+let country = 'Finland'
+
+console.log(country.toUpperCase())    // FINLAND
+toLowerCase(): this method changes the string to lowercase letters.
+let string = 'JavasCript'
+
+console.log(string.toLowerCase())     // javascript
+
+let firstName = 'Asabeneh'
+
+console.log(firstName.toLowerCase())  // asabeneh
+
+let country = 'Finland'
+
+console.log(country.toLowerCase())   // finland
+substr(): It takes two arguments, the starting index and number of characters to slice.
+let string = 'JavaScript'
+console.log(string.substr(4,6))    // Script
+
+let country = 'Finland'
+console.log(country.substr(3, 4))   // land
+substring(): It takes two arguments, the starting index and the stopping index but it doesn't include the character at the stopping index.
+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
+split(): The split method splits a string at a specified place.
+let string = '30 Days Of JavaScript'
+
+console.log(string.split())     // Changes to an array -> ["30 Days Of JavaScript"]
+console.log(string.split(' '))  // Split to an array at space -> ["30", "Days", "Of", "JavaScript"]
+
+let firstName = 'Asabeneh'
+
+console.log(firstName.split())    // Change to an array - > ["Asabeneh"]
+console.log(firstName.split(''))  // Split to an array at each letter ->  ["A", "s", "a", "b", "e", "n", "e", "h"]
+
+let countries = 'Finland, Sweden, Norway, Denmark, and Iceland'
+
+console.log(countries.split(','))  // split to any array at comma -> ["Finland", " Sweden", " Norway", " Denmark", " and Iceland"]
+console.log(countries.split(', ')) //  ["Finland", "Sweden", "Norway", "Denmark", "and Iceland"]
+trim(): Removes trailing space in the beginning or the end of a string.
+let string = '   30 Days Of JavaScript   '
+
+console.log(string)
+console.log(string.trim(' '))
+
+let firstName = ' Asabeneh '
+
+console.log(firstName)
+console.log(firstName.trim())  // still removes spaces at the beginning and the end of the string
+   30 Days Of JavasCript   
+30 Days Of JavasCript
+  Asabeneh 
+Asabeneh
+includes(): It takes a substring argument and it checks if substring argument exists in the string. includes() returns a boolean. If a substring exist in a string, it returns true, otherwise it returns false.
+let string = '30 Days Of JavaScript'
+
+console.log(string.includes('Days'))     // true
+console.log(string.includes('days'))     // false - it is case sensitive!
+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
+replace(): takes as a parameter the old substring and a new substring.
+string.replace(oldsubstring, newsubstring)
+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
+charAt(): Takes index and it returns the value at that index
+string.charAt(index)
+let string = '30 Days Of JavaScript'
+console.log(string.charAt(0))        // 3
+
+let lastIndex = string.length - 1
+console.log(string.charAt(lastIndex)) // t
+charCodeAt(): Takes index and it returns char code (ASCII number) of the value at that index
+string.charCodeAt(index)
+let string = '30 Days Of JavaScript'
+console.log(string.charCodeAt(3))        // D ASCII number is 68
+
+let lastIndex = string.length - 1
+console.log(string.charCodeAt(lastIndex)) // t ASCII is 116
+indexOf(): 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
+string.indexOf(substring)
+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
+lastIndexOf(): 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
+//syntax
+string.lastIndexOf(substring)
+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
+concat(): it takes many substrings and joins them.
+string.concat(substring, substring, substring)
+let string = '30'
+console.log(string.concat("Days", "Of", "JavaScript")) // 30DaysOfJavaScript
+
+let country = 'Fin'
+console.log(country.concat("land")) // Finland
+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).
+//syntax
+string.startsWith(substring)
+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
+endsWith: it takes a substring as an argument and it checks if the string ends with that specified substring. It returns a boolean(true or false).
+string.endsWith(substring)
+let string = 'Love is the most powerful feeling in the world'
+
+console.log(string.endsWith('world'))         // true
+console.log(string.endsWith('love'))          // false
+console.log(string.endsWith('in the world')) // true
+
+let country = 'Finland'
+
+console.log(country.endsWith('land'))         // true
+console.log(country.endsWith('fin'))          // false
+console.log(country.endsWith('Fin'))          //  false
+search: it takes a substring as an argument and it returns the index of the first match. The search value can be a string or a regular expression pattern.
+string.search(substring)
+let string = 'I love JavaScript. If you do not love JavaScript what else can you love.'
+console.log(string.search('love'))          // 2
+console.log(string.search(/javascript/gi))  // 7
+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 expression pattern looks like. It starts with / sign and ends with / sign.
+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
+Match syntax
+
+// syntax
+string.match(substring)
+let string = 'I love JavaScript. If you do not love JavaScript what else can you love.'
+console.log(string.match('love'))
+["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 a regular expression. This is not the regular expression section, do not panic! We will cover regular expressions later on.
+
+let txt = 'In 2019, I ran 30 Days of Python. Now, in 2020 I am 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(txt.match(regEx))  // ["2", "0", "1", "9", "3", "0", "2", "0", "2", "0"]
+console.log(txt.match(/\d+/g)) // ["2019", "30", "2020"]
+repeat(): it takes a number as argument and it returns the repeated version of the string.
+string.repeat(n)
+let string = 'love'
+console.log(string.repeat(10)) // lovelovelovelovelovelovelovelovelovelove
+Checking Data Types and Casting
+Checking Data Types
+To check the data type of a certain variable we use the typeof method.
+
+Example:
+
+// Different javascript data types
+// Let's declare different data types
+
+let firstName = 'Asabeneh'      // string
+let lastName = 'Yetayeh'        // string
+let country = 'Finland'         // string
+let city = 'Helsinki'           // string
+let age = 250                   // number, it is not my real age, do not worry about it
+let job                         // undefined, because a value was not assigned
+
+console.log(typeof 'Asabeneh')  // string
+console.log(typeof firstName)   // string
+console.log(typeof 10)          // number
+console.log(typeof 3.14)        // number
+console.log(typeof true)        // boolean
+console.log(typeof false)       // boolean
+console.log(typeof NaN)         // number
+console.log(typeof job)         // undefined
+console.log(typeof undefined)   // undefined
+console.log(typeof null)        // object
+Changing Data Type (Casting)
+Casting: Converting one data type to another data type. We use parseInt(), parseFloat(), Number(), + sign, str() When we do arithmetic operations string numbers should be first converted to integer or float if not it returns an error.
+String to Int
+We can convert string number to a number. Any number inside a quote is a string number. An example of a string number: '10', '5', etc. We can convert string to number using the following methods:
+
+parseInt()
+Number()
+Plus sign(+)
+let num = '10'
+let numInt = parseInt(num)
+console.log(numInt) // 10
+let num = '10'
+let numInt = Number(num)
+
+console.log(numInt) // 10
+let num = '10'
+let numInt = +num
+
+console.log(numInt) // 10
+String to Float
+We can convert string float number to a float number. Any float number inside a quote is a string float number. An example of a string float number: '9.81', '3.14', '1.44', etc. We can convert string float to number using the following methods:
+
+parseFloat()
+Number()
+Plus sign(+)
+let num = '9.81'
+let numFloat = parseFloat(num)
+
+console.log(numFloat) // 9.81
+let num = '9.81'
+let numFloat = Number(num)
+
+console.log(numFloat) // 9.81
+let num = '9.81'
+let numFloat = +num
+
+console.log(numFloat) // 9.81