Merge pull request #1 from AayushYadavz/main

Dataypes Summary

01_Basics/05_datatypes-summary.js

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+/* Data Types are divided into 2 Types,
+1. Primitive Data Type &
+2. Non-Primitive Data Type
+
+Note : How Data is stored and How data is accsessed from the memory on the basis of this
+categorisation of data is done. 
+
+Note : JavaScript is dynamically typed. 
+
+----------------------------------------------------------------------------------------------------------
+
+1. Primitive Data Type : 7 Types : String, Number, Boolean, Symbol, Null, undefined, BigInt. (These 
+are call by value) */
+
+const score = 100
+const scoreValue = 100.3
+// Both comes into number category there is noting like float value for decimal e.t.c like other languages.
+const isLoogedIn = true // Boolean
+const outsideTemp = null // Null
+let weather; // OR let weather = undefined // Undefined
+// Symbol,
+const id = Symbol('123')
+const anotherId = Symbol('123') 
+/* The return type for both will be the data type (Symbol) and both id & anotherId treated diffrently.
+To check, */
+console.log(id === anotherId); // false
+const bigNumber = 23873847283748289483n // By writing n at the end it gets converted into BigInt.
+
+
+/* -------------------------------------------------------------------------------------------------------
+
+2. Reference Type (Non-Primitive) : array, objects, functions. */
+
+// Array,
+const heros = ["ironman", "spiderman", "batman"];
+// Objects,
+let myObj = { // We can store them into a Variable
+    name: "Ayush",
+    age: 21, 
+} // The code inside these curly braces is object.
+// Function,
+const myFunction = function (){ // Defintion stored into a variable
+    console.log("Hello World");
+}
+
+/* ------------------------------------------------------------------------------------------------------
+
+Checking Data Types of all, 
+Primitive, */
+console.log(typeof scoreValue); // number
+console.log(typeof isLoogedIn); // boolean
+console.log(typeof outsideTemp); // object
+console.log(typeof weather); // undefined
+console.log(typeof anotherId); // symbol
+console.log(typeof bigNumber); // bigint
+
+// No Primitive,
+console.log(typeof heros); // Object
+console.log(typeof myObj); // object
+console.log(typeof myFunction); // function
+

01_Basics/06_stackAndHeap.js

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+// 6. Stack & Heap
+
+// * Some notes also available in note book with Diagram. Photo available in readme.md
+
+// Example of Stack,
+let myYoutubeName = "ayushyadavz" // Primitive Type so myYoutubeName will go into stack.
+let anotherName = myYoutubeName // This will have the copy value of myYoutubeName.
+anotherName = "amanyadavz" // It's value will go in stack.
+console.log(myYoutubeName); // Output : ayushyadavz (Original value did not change)
+console.log(anotherName); // Output : amanyadavz (Only Copy value is changed)
+/* So, here we have changed the copy not the original value.
+
+---------------------------------------------------------------------------------------- */
+
+// Example of Heap,
+let userOne = { // UserOne will go into Stack. (Primitive)
+    email: "user@google.com",
+    upi: "user@ybl"
+} // items between {} will go into Heap. (Non-Primitive)
+let userTwo = userOne // userTwo will get reference from original value.
+userTwo.email = "ayush@google.com"
+console.log(userOne.email); // Output : ayush@google.com
+console.log(userTwo.email); // Output : ayush@google.com
+// (Original Value gets changed)

01_Basics/07_strings.js

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+/* 7. Strings
+
+(i) Concatenation in Strings, */
+const name = "Ayush"
+const repoCount = 19
+// Outdated Syntax,
+console.log(name + repoCount + " etc."); // Output : Ayush19 etc.
+// Modern day Syntax,
+console.log(`My name is ${name} and I have total ${repoCount} repositories on GiHub.`);
+// Output : My name is Ayush and I have total 19 repositories on GiHub.
+/* Note: Benifits of this syntax is that we can use methods like, ${name.toUpperCase} e.t.c.
+
+-------------------------------------------------------------------------------------------------- */
+
+// (ii) One more way of declaring strings,
+const gameName = new String('SuperMario') /* When we run this in Browser's console we can see
+some interesting things there.
+
+Some Methods of String, */
+// (a) Accessing 0th key of gameName,
+console.log(gameName[0]); // Output : S
+// (b) Accessing prototype,
+console.log(gameName.__proto__); // Output : {}
+
+// (c) Accessing methods of Prototype,
+console.log(gameName.length); // Output : 10
+console.log(gameName.toUpperCase()); // Output : SUPERMARIO 
+// This will not change our original string cause as we know about Stack.
+console.log(gameName.charAt(3)); // Output : e
+console.log(gameName.indexOf('M')); // Output : 5
+
+const discordName = "hitesh-hc"
+console.log(discordName.length); // Output : 9
+const newString = discordName.substring(0, 4) // It will not include the 4th one.
+console.log(newString); // Output : hite
+
+const anotherString = discordName.slice(-8, 4)
+console.log(anotherString); /* Output : ite
+Note : We cannot give negative values in substring but we can give negative value in slice. */
+
+const oneNewString = "    hitesh    "
+console.log(oneNewString.trim()) // Output : hitesh (will remove that spaces around the string.)
+
+const url = "https://ayush.com/ayush%20yadav"
+console.log(url.replace('%20', '-')); /* Output : https://ayush.com/ayush-yadav
+Also, */
+console.log(url.includes('ayush')) // Output : true
+
+console.log(discordName.split('-')); /* Output : [ 'hitesh', 'hc' ] (Converted into array with
+two strings) */
+
+
+
+

01_Basics/08_nums_and_maths.js

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+/* 8. Numbers And Maths
+
+(i) Numbers, 
+When Javascript automatically defines the data type, */
+const balance = 400
+// console.log(balance); // Output: 400
+// Note: Here Javascript automatically detected that the score type is number.
+
+// But we can also define explicitely the data type,
+const newBalance = new Number(400)
+// console.log(newBalance); // Output: [Number: 400]
+// Note: When we do this in browser console the we can see the methods. 
+
+// ---------------------------------------------------------------------------------------------------------
+
+// Some Methods,
+// console.log(newBalance.toString()); // Output: 400 
+// Note: When we will check it's typeof the we will see that it is changed into strings.
+// console.log(newBalance.toString().length); // Output: 3 (cause 400 has 3 chracters.)
+
+// console.log(newBalance.toFixed(2)); // Output: 400.00
+
+const otherNumbers = 123.8966
+// console.log(otherNumbers.toPrecision(3)); // Output: 124
+const otherNum = 23.8966
+// console.log(otherNum.toPrecision(3)); // Output: 23.9
+// Note: It means we want precise value but on how many values we want to focus.
+
+const hundreds = 1000000
+// console.log(hundreds.toLocaleString('en-IN')); // Output: 10,00,000 (converted accor. to IN standards.)
+
+/* *******************************************MATHS******************************************************* 
+
+(ii) Maths, */
+console.log(Math); /* Output: Object [Math] {} 
+Note: When we run this console.log(Math) in browser's console we will get many value inside object. */
+
+console.log(Math.abs(-4)); // Output: 4 (Changes only minus values in plus)
+
+console.log(Math.round(4.6)); // Output: 5
+console.log(Math.round(4.4)); // Output: 4
+console.log(Math.ceil(4.2)); // Output: 5 (Choose top value)
+console.log(Math.floor(4.9)); // Output: 4 (Choose lowest value)
+
+console.log(Math.min(3, 2, 4, 6)); /* Output: 2 (Tells min value)
+Note: There is also "max". */
+
+console.log(Math.random()); // Output: 0.36675387800250636 (Gives random numbers between 0 & 1)
+console.log((Math.random()*10) + 1); // Now numbers will range from 1 to 9
+console.log(Math.floor(Math.random()*10) + 1); // Round offs the Random numbers at lowest value.
+
+const min = 10
+const max = 20
+console.log(Math.floor(Math.random() * (max - min + 1)) + min);
+// Note: (max - min) to get a range, (+ 1) to avoid zero, (+ min) to get minimum value to this.  

01_Basics/09_datesIn.js

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+/* 9. Dates
+
+Note: Our declared Dates has been calculated from 1 January 1970.
+Note: Dates has been calculated usually in Milliseconds. */
+
+let myDate = new Date();
+console.log(myDate); /* Output: 2024-04-24T08:15:11.671Z
+
+--------------------------------------------------------------------------------------
+
+Conversion of Dates in readable form,
+Some Methods, */
+console.log(myDate.toString()); // Output: Wed Apr 24 2024 13:47:36 GMT+0530 (India Standard Time)
+console.log(myDate.toDateString()); // Output: Wed Apr 24 2024
+console.log(myDate.toLocaleString()); // Output: 24/4/2024, 1:49:14 pm
+console.log(myDate.toJSON()); // Output: 2024-04-24T08:20:04.530Z
+console.log(myDate.toISOString()); // Output: 2024-04-24T08:21:49.915Z
+console.log(myDate.toLocaleDateString()); /* Output: 24/4/2024
+
+--------------------------------------------------------------------------------------
+
+Typeof Date, */
+console.log(typeof myDate); /* Output: Object
+
+--------------------------------------------------------------------------------------
+
+Declaring a new or a specific date, */
+// let myCreatedDate = new Date(2002, 10, 24) // Months starts with 0 in JS.
+// console.log(myCreatedDate.toDateString()); // Output: Sun Nov 24 2002
+// let myCreatedDate = new Date(2002, 10, 24, 5, 3)
+// console.log(myCreatedDate.toLocaleString()); // Output: 24/11/2002, 5:03:00 am
+let myCreatedDate = new Date("11-24-2002")
+console.log(myCreatedDate.toLocaleString()); /* Output: 24/11/2002, 5:30:00 am
+
+-------------------------------------------------------------------------------------- */
+
+let myTimeStamp = Date.now()
+console.log(myTimeStamp); // Output: 1713948664801 (Millisecond value from 1 Jan 1970 to current)
+console.log(myCreatedDate.getTime()); /* Output: 1038076200000 
+So now we can easily compare 1713948664801 and 1038076200000.
+
+Converting it into seconds, */
+console.log(Math.floor(Date.now()/1000)); // Output: 1713950199
+
+let myDates = new Date()
+console.log(myDates);
+console.log(myDates.getDay()); // Output: 3
+console.log(myDates.getMonth() + 1); /* Output: 4
+
+----------------------------------------------------------------------------------------
+
+Some other syntax, */
+`${myDates.getDay()} and the time is`
+// We can completely define what we want,
+myDates.toLocaleString('default', {
+    weekday: "long"
+})
+
+
+
+

02_Basics/01_arrays.js

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+/* 1. Arrays
+
+(i) Declaring Array, */
+const myArr = [0, 1, 2, 3, 4]
+// console.log(myArr[2]); // Output: 2 | Accsessing value of an Array.
+// Note: Array indexing starts from Zero.
+const heros = ["Thor", "IronMan", "SpiderMan"]
+// console.log(heros); // Output: [ 'Thor', 'IronMan', 'SpiderMan' ]
+const myArr2 = new Array(1, 2, 3, 4)
+// console.log(myArr2); // Output: [ 1, 2, 3, 4 ]
+/* Note: Run const numbers = [1, 2, 3, 4] in browser's console to see prototype access in Arrays.
+
+-----------------------------------------------------------------------------------------------------
+
+(ii) Array Methods, */
+myArr.push(6)
+// console.log(myArr); // Output: [ 0, 1, 2, 3, 4, 6 ] | Pushes element in the end of the array.
+myArr.pop()
+// console.log(myArr); // Output: [ 0, 1, 2, 3, 4 ] | Removes element from the end of the array.
+myArr.unshift(9)
+// console.log(myArr); // Output: [ 9, 0, 1, 2, 3, 4 ] | Adds element to the starting of the array.
+myArr.shift()
+// console.log(myArr); // Output: [ 0, 1, 2, 3, 4 ] | Removes element from the starting of the array.
+
+// console.log(myArr.includes(9)); // Output: false
+
+// console.log(myArr.indexOf(4)); // Output: 4 
+// Note: Indexing starts from Zero.
+// console.log(myArr.indexOf(9)); // Output: -1
+// Asking any value which doesn't exist in index gives you -1.
+
+const newArr = myArr.join()
+// console.log(newArr); // Output: 0,1,2,3,4
+// console.log(typeof newArr); // Output: string
+/* Note: .join binds and converts array into strings.
+
+-----------------------------------------------------------------------------------------------------
+
+(iii) slice, splice (Methods) */
+console.log("A ", myArr); // Output: A  [ 0, 1, 2, 3, 4 ]
+const myNewArr1 = myArr.slice(1, 3) /* Include value at index 1 and 2 but don't 
+include value at index 3. */
+console.log(myNewArr1); // Output: [ 1, 2 ]
+console.log("B ", myArr); // Output: B  [ 0, 1, 2, 3, 4 ]
+// Note: As we can see using slice doesn't affect original array.
+
+const myNewArr2 = myArr.splice(1, 3)
+console.log(myNewArr2); // Output: [ 1, 2, 3 ]
+console.log("C ", myArr); // Output: C  [ 0, 4 ]
+// Note: But in splice we can see it removes the elements and manipulates the original array.
+

02_Basics/02_arrays.js

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+// 2. Arrays
+
+// (i) Methods to merge Arrays,
+const marvel_heros = ["Thor", "Hulk", "Loki"]
+const dc_heros = ["Flash", "Superman", "Batman"]
+// marvel_heros.push(dc_heros)
+console.log(marvel_heros); // Output: [ 'Thor', 'Hulk', 'Loki', [ 'Flash', 'Superman', 'Batman' ] ]
+/* Note: In this dc_heros array has been taken as an 4th element in marvel_heros array.
+And this is not a good practice or a good syntax. */
+
+const all_heros = marvel_heros.concat(dc_heros)
+console.log(all_heros); // Output: [ 'Thor', 'Hulk', 'Loki', 'Flash', 'Superman', 'Batman' ]
+// Note: .push pushes on existing array & .concat returns a new array.
+
+const all_new_heros = [...marvel_heros, ...dc_heros]
+console.log(all_new_heros); // Output: [ 'Thor', 'Hulk', 'Loki', 'Flash', 'Superman', 'Batman' ]
+/* Note: This methods is used more, cause we can add multiple values in this ([..., ..., ...]).
+
+----------------------------------------------------------------------------------------------------*/
+
+const another_array = [1, 2, 3, [4, 5], 3, 4, [9, [4, 3]]]
+const another_new_array = another_array.flat(Infinity)
+console.log(another_new_array); // Output: [1, 2, 3, 4, 5, 3, 4, 9, 4, 3]
+/* Note: All the values spreaded into a Array.
+
+----------------------------------------------------------------------------------------------------
+
+(ii) Converting into Array, */
+console.log(Array.isArray("Ayush")); // Output: false | Ayush is not an Array.
+// Converting it into an Array,
+console.log(Array.from("Ayush")); // Output: [ 'A', 'y', 'u', 's', 'h' ] | Converted string into Array.
+// Objects into Array,
+console.log(Array.from({name: "Ayush"})); // Output: [] | Returns an empty array.
+
+const score1 = 100
+const score2 = 200
+const score3 = 300
+console.log(Array.of(score1, score2, score3)); // Output: [ 100, 200, 300 ]