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loianeloiane
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chapter 3: arrays
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‎package.json‎

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"version": "4.0.0",
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"description": "Learning JavaScript Data Structures and Algorithms",
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"scripts": {
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"build:ts": "tsc -p tsconfig.json",
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"test": "echo \"Error: no test specified\" && exit 1"
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},
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"author": "Loiane Groner",

‎src/01-intro/08-typescript.js‎

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// Path: src/01-intro/08-typescript.ts
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var myName = 'Packt';
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let myName = 'Packt';
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// myName = 10; // commented to avoid error
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/* Type inference */
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var age = 20; // number
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var existsFlag = true; // boolean
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var language = 'JavaScript'; // string
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var favoriteLanguage;
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var langs = ['JavaScript', 'Ruby', 'Python'];
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let age = 20; // number
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let existsFlag = true; // boolean
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let language = 'JavaScript'; // string
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let favoriteLanguage;
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let langs = ['JavaScript', 'Ruby', 'Python'];
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favoriteLanguage = langs[0];
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function printName(person) {
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console.log(person.name);
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}
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var john = { name: 'John', age: 21 };
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var mary = { name: 'Mary', age: 21, phone: '123-45678' };
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const john = { name: 'John', age: 21 };
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const mary = { name: 'Mary', age: 21, phone: '123-45678' };
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printName(john);
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printName(mary);
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class MyObject {
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age;
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constructor(age) {
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this.age = age;
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}
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compareTo(b) {
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if (this.age === b.age) {
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return 0;
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}
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return this.age > b.age ? 1 : -1;
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}
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}
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/* Enums */
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var Compare;
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(function (Compare) {
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Compare[Compare["LESS_THAN"] = -1] = "LESS_THAN";
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Compare[Compare["BIGGER_THAN"] = 1] = "BIGGER_THAN";
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Compare[Compare["EQUALS"] = 0] = "EQUALS";
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})(Compare || (Compare = {}));
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function compareTo(a, b) {
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if (a.age === b.age) {
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return Compare.EQUALS;
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}
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return a.age > b.age ? Compare.BIGGER_THAN : Compare.LESS_THAN;
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}

‎src/01-intro/08-typescript.ts‎

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favoriteLanguage = langs[0];
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/* Interfaces as type */
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interface Person {
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interface Friend {
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name: string;
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age: number;
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}
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function printName(person: Person) {
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function printName(person: Friend) {
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console.log(person.name);
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}
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‎src/03-array/01-arrays.js‎

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// Path: src/03-array/01-arrays.js
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/* Arrays Intro */
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const averageTempJan = 12;
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const averageTempFeb = 15;
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const averageTempMar = 18;
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const averageTempApr = 20;
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const averageTempMay = 25;
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const averageTemp = [12, 15, 18, 20, 25];
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// or
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averageTemp[0] = 12;
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averageTemp[1] = 15;
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averageTemp[2] = 18;
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averageTemp[3] = 20;
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averageTemp[4] = 25;
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console.log('averageTempJan', averageTempJan);
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console.log('averageTempFeb', averageTempFeb);
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console.log('averageTempMar', averageTempMar);
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console.log('averageTempApr', averageTempApr);
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console.log('averageTempMay', averageTempMay);
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console.log('averageTemp[0]', averageTemp[0]);
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console.log('averageTemp[1]', averageTemp[1]);
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console.log('averageTemp[2]', averageTemp[2]);
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console.log('averageTemp[3]', averageTemp[3]);
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console.log('averageTemp[4]', averageTemp[4]);
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/* Creating and initializing arrays */
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let daysOfWeek = new Array(); // {1}
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daysOfWeek = new Array(7); // {2}
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daysOfWeek = new Array('Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday'); // {3}
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// preferred
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daysOfWeek = []; // {4}
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daysOfWeek = ['Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday']; // {5}
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console.log('daysOfWeek.length', daysOfWeek.length); // output: 7
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for (let i = 0; i < daysOfWeek.length; i++) {
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console.log(`daysOfWeek[${i}]`, daysOfWeek[i]);
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}
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/* fibonacci numbers */
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// Fibonacci: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, ...
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const fibonacci = []; // {1}
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fibonacci[1] = 1; // {2}
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fibonacci[2] = 1; // {3}
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// create the fibonacci sequence starting from the 3rd element
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for (let i = 3; i < 20; i++) {
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fibonacci[i] = fibonacci[i - 1] + fibonacci[i - 2]; // //{4}
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}
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// display the fibonacci sequence
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for (let i = 1; i < fibonacci.length; i++) { // {5}
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console.log(`fibonacci[${i}]`, fibonacci[i]); // {6}
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}
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// instead of {5} and {6} we can use
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console.log('fibonacci', fibonacci);
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// Using the for..in loop
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for (const i in fibonacci) {
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console.log(`fibonacci[${i}]`, fibonacci[i]);
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}
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// Using the for..of loop
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for (const value of fibonacci) {
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console.log('value', value);
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}
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// to see the output of this file use the command: node src/03-array/01-arrays.js

‎src/03-array/01-arrays.ts‎

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// Path: src/03-array/01-arrays.ts
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/* Arrays Intro */
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const averageTempJan = 12;
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const averageTempFeb = 15;
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const averageTempMar = 18;
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const averageTempApr = 20;
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const averageTempMay = 25;
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const averageTemp = [12, 15, 18, 20, 25];
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// or
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averageTemp[0] = 12;
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averageTemp[1] = 15;
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averageTemp[2] = 18;
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averageTemp[3] = 20;
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averageTemp[4] = 25;
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console.log('averageTempJan', averageTempJan);
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console.log('averageTempFeb', averageTempFeb);
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console.log('averageTempMar', averageTempMar);
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console.log('averageTempApr', averageTempApr);
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console.log('averageTempMay', averageTempMay);
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console.log('averageTemp[0]', averageTemp[0]);
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console.log('averageTemp[1]', averageTemp[1]);
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console.log('averageTemp[2]', averageTemp[2]);
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console.log('averageTemp[3]', averageTemp[3]);
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console.log('averageTemp[4]', averageTemp[4]);
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/* Creating and initializing arrays */
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let daysOfWeek = new Array(); // {1}
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daysOfWeek = new Array(7); // {2}
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daysOfWeek = new Array('Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday'); // {3}
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// preferred
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daysOfWeek = []; // {4}
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daysOfWeek = ['Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday']; // {5}
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console.log('daysOfWeek.length', daysOfWeek.length); // output: 7
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for (let i = 0; i < daysOfWeek.length; i++) {
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console.log(`daysOfWeek[${i}]`, daysOfWeek[i]);
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}
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/* fibonacci numbers */
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// Fibonacci: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, ...
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const fibonacci = []; // {1}
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fibonacci[1] = 1; // {2}
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fibonacci[2] = 1; // {3}
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// create the fibonacci sequence starting from the 3rd element
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for (let i = 3; i < 20; i++) {
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fibonacci[i] = fibonacci[i - 1] + fibonacci[i - 2]; // //{4}
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}
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// display the fibonacci sequence
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for (let i = 1; i < fibonacci.length; i++) { // {5}
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console.log(`fibonacci[${i}]`, fibonacci[i]); // {6}
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}
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// instead of {5} and {6} we can use
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console.log('fibonacci', fibonacci);
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// Using the for..in loop
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for (const i in fibonacci) {
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console.log(`fibonacci[${i}]`, fibonacci[i]);
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}
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// Using the for..of loop
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for (const value of fibonacci) {
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console.log('value', value);
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}
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// to see the output of this file use the command: node src/03-array/01-arrays.ts

‎src/03-array/02-adding-removing-elements.js‎

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// Path: src/03-array/02-adding-removing-elements.js
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// @ts-ignore
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let numbers = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
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numbers[numbers.length] = 10;
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// using push method
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numbers.push(11);
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numbers.push(12, 13);
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// inserting elements at the beginning
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// @ts-ignore
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Array.prototype.insertAtBeginning = function (value) {
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for (let i = this.length; i >= 0; i--) {
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this[i] = this[i - 1];
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}
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this[0] = value;
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};
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// @ts-ignore
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numbers.insertAtBeginning(-1);
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// using unshift method
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numbers.unshift(-2);
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numbers.unshift(-4, -3);
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// removing elements from the end
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numbers.pop(); // number 13 is removed
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// console.log('Removed element: ', numbers.pop()); // Removed element: 13
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console.log('array length: ', numbers.length); // array length: 17
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// removing elements from the beginning
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for (let i = 0; i < numbers.length; i++) {
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// numbers[i] = numbers[i + 1];
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}
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// removing elements from the beginning - educational purposes only
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// @ts-ignore
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Array.prototype.reIndex = function (myArray) {
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const newArray = [];
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for (let i = 0; i < myArray.length; i++) {
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if (myArray[i] !== undefined) {
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newArray.push(myArray[i]);
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}
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}
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return newArray;
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}
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// remove first position manually and reIndex
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// @ts-ignore
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Array.prototype.removeFromBeginning = function () {
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for (let i = 0; i < this.length; i++) {
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this[i] = this[i + 1];
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}
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// @ts-ignore
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return this.reIndex(this);
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};
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// @ts-ignore
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// numbers = numbers.removeFromBeginning();
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// using shift method
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numbers.shift();
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console.log('numbers after shift: ', numbers);
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console.log('array length: ', numbers.length); // array length: 16
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// adding and removing elements from a specific position
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// using the splice method
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numbers.splice(5, 3); // removes 3 elements starting from the 5th position
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console.log('numbers: ', numbers); // numbers: [ -3, -2, -1, 0, 1, 5, 6, 7, 8, 9, 10, 11, 12 ]
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// adding elements, 2, 3 and 4 at the 5th position
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numbers.splice(5, 0, 2, 3, 4);
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// to see the output of this file use the command: node src/03-array/02-adding-removing-elements.js

‎src/03-array/02-adding-removing-elements.ts‎

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// Path: src/03-array/02-adding-removing-elements.ts
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// @ts-ignore
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let numbers = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
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numbers[numbers.length] = 10;
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// using push method
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numbers.push(11);
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numbers.push(12, 13);
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// inserting elements at the beginning
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// @ts-ignore
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Array.prototype.insertAtBeginning = function (value) {
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for (let i = this.length; i >= 0; i--) {
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this[i] = this[i - 1];
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}
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this[0] = value;
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};
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// @ts-ignore
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numbers.insertAtBeginning(-1);
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// using unshift method
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numbers.unshift(-2);
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numbers.unshift(-4, -3);
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// removing elements from the end
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numbers.pop(); // number 13 is removed
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// console.log('Removed element: ', numbers.pop()); // Removed element: 13
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console.log('array length: ', numbers.length); // array length: 17
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// removing elements from the beginning
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for (let i = 0; i < numbers.length; i++) {
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// numbers[i] = numbers[i + 1];
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}
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// removing elements from the beginning - educational purposes only
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// @ts-ignore
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Array.prototype.reIndex = function (myArray) {
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const newArray = [];
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for (let i = 0; i < myArray.length; i++) {
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if (myArray[i] !== undefined) {
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newArray.push(myArray[i]);
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}
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}
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return newArray;
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}
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// remove first position manually and reIndex
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// @ts-ignore
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Array.prototype.removeFromBeginning = function () {
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for (let i = 0; i < this.length; i++) {
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this[i] = this[i + 1];
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}
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// @ts-ignore
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return this.reIndex(this);
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};
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// @ts-ignore
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// numbers = numbers.removeFromBeginning();
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// using shift method
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numbers.shift();
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console.log('numbers after shift: ', numbers);
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console.log('array length: ', numbers.length); // array length: 16
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// adding and removing elements from a specific position
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// using the splice method
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numbers.splice(5, 3); // removes 3 elements starting from the 5th position
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console.log('numbers: ', numbers); // numbers: [ -3, -2, -1, 0, 1, 5, 6, 7, 8, 9, 10, 11, 12 ]
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// adding elements, 2, 3 and 4 at the 5th position
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numbers.splice(5, 0, 2, 3, 4);
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// to see the output of this file use the command: node src/03-array/02-adding-removing-elements.ts

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