Asabeneh
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<div align="center">
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<h1> 30 Days Of JavaScript</h1>
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<a class="header-badge" target="_blank" href="https://github.com/Asabeneh/30DaysOfJavaScript">
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<img alt="GitHub stars" src="https://img.shields.io/github/stars/asabeneh/30DaysOfJavaScript?style=social">
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</a>
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<a class="header-badge" target="_blank" href="https://www.linkedin.com/in/asabeneh/">
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<img src="https://img.shields.io/badge/style--5eba00.svg?label=LinkedIn&logo=linkedin&style=social">
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</a>
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<a class="header-badge" target="_blank" href="https://twitter.com/Asabeneh">
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<img alt="Twitter Follow" src="https://img.shields.io/twitter/follow/asabeneh?style=social">
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</a>
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<sub>Author:
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<a href="https://www.linkedin.com/in/asabeneh/" target="_blank">Asabeneh Yetayeh</a><br>
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<small> January, 2020</small>
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</sub>
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</div>
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[<< Day 7](https://github.com/Asabeneh/30DaysOfJavaScript/blob/master/09_Day/09_day_function_programming.md) | [Day 9 >>](#)
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- [Day 8](#day-8)
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- [Scope](#scope)
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- [Window Scope](#window-scope)
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- [Global scope](#global-scope)
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- [Local scope](#local-scope)
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- [📔 Object](#%f0%9f%93%94-object)
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- [Creating an empty object](#creating-an-empty-object)
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- [Creating an objecting with values](#creating-an-objecting-with-values)
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- [Getting values from an object](#getting-values-from-an-object)
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- [Creating object methods](#creating-object-methods)
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- [Setting new key for an object](#setting-new-key-for-an-object)
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- [Object Methods](#object-methods)
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- [Getting object keys using Object.keys()](#getting-object-keys-using-objectkeys)
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- [Getting object values using Object.values()](#getting-object-values-using-objectvalues)
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- [Getting object keys and values using Object.entries()](#getting-object-keys-and-values-using-objectentries)
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- [Checking properties using hasOwnProperty()](#checking-properties-using-hasownproperty)
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- [💻 Exercises](#%f0%9f%92%bb-exercises)
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# Day 8
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## Scope
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Variable is the fundamental part in programming. We declare variable to store different data types. To declare a variable we use the key word _var_, _let_ and _const_. A variable can declared at different scope. In this section we will see the scope, scope of variables when we use var or let.
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Variables scopes can be:
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- Window
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- Global
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- Local
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Variable can be declared globally or locally or window scope. We will see both global and local scope.
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Anything declared without let, var or const is scoped at window level.
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Let us image we have a scope.js file.
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### Window Scope
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Without using console.log() open your browser and check, you will see the value of a and b if you write a or b on the browser. That means a and b are already available in the window.
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```js
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//scope.js
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a = 'JavaScript' // is a window scope this found anywhere
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b = 10 // this is a window scope variable
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function letsLearnScope() {
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console.log(a, b)
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if (true) {
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console.log(a, b)
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}
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}
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console.log(a, b) // accessible
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```
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### Global scope
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A globally declared variable can be access every where in the same file. But the term global is relative. It can be global to the file or it can be global relative to some block of codes.
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```js
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//scope.js
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let a = 'JavaScript' // is a global scope it will be found anywhere in this file
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let b = 10 // is a global scope it will be found anywhere in this file
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function letsLearnScope() {
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console.log(a, b) // JavaScript 10, accessible
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if (true) {
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let a = 'Python'
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let b = 100
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console.log(a, b) // Python 100
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}
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console.log(a, b)
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}
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letsLearnScope()
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console.log(a, b) // JavaScript 10, accessible
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```
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### Local scope
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A local declared variable can be access only certain block code.
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```js
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//scope.js
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let a = 'JavaScript' // is a global scope it will be found anywhere in this file
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let b = 10 // is a global scope it will be found anywhere in this file
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function letsLearnScope() {
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console.log(a, b) // JavaScript 10, accessible
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let c = 30
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if (true) {
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// we can access from the function and outside the function but
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// variables declared inside the if will not be accessed outside the if block
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let a = 'Python'
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let b = 20
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let d = 40
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console.log(a, b, c) // Python 20 30
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}
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// we can not access c because c's scope is only the if block
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console.log(a, b)
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}
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letsLearnScope()
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console.log(a, b) // JavaScript 10, accessible
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```
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Now, you have an understanding of scope. A variable declared with *var* only scoped to function but variable declared with *let* or *const* is block scope(function block, if block, loop etc)
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```js
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//scope.js
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function letsLearnScope() {
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var gravity = 9.81
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console.log(gravity)
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}
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// console.log(gravity), Uncaught ReferenceError: gravity is not defined
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if (true){
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var gravity = 9.81
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console.log(gravity) // 9.81
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}
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console.log(gravity) // 9.81
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for(var i = 0; i < 3; i++){
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console.log(i) // 1, 2, 3
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}
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console.log(i)
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```
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In ES6 and above there is *let* and *const*, so you will suffer from the sneakiness of *var*. When we use *let* our variable is block scope and it will not infect other parts of our code.
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```js
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//scope.js
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function letsLearnScope() {
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// you can use let or const, but gravity is constant I prefer to use const
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const gravity = 9.81
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console.log(gravity)
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}
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// console.log(gravity), Uncaught ReferenceError: gravity is not defined
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if (true){
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const gravity = 9.81
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console.log(gravity) // 9.81
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}
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// console.log(gravity), Uncaught ReferenceError: gravity is not defined
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for(let i = 0; i < 3; i++){
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console.log(i) // 1, 2, 3
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}
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// console.log(i), Uncaught ReferenceError: gravity is not defined
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```
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The scope *let* and *const* is the same. The difference is only reassigning. We can not change or reassign the value of const variable.
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## 📔 Object
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Everything can be an object and objects do have properties and properties have values.
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Creating an object literal. To create an object literal, we use two curly brackets.
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### Creating an empty object
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An empty object
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```js
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const person = {}
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```
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### Creating an objecting with values
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Now, the person object has firstName, lastName, age, location, skills and isMarried properties. The value of properties or keys could be a string, number, boolean, an object, null, undefined or a function.
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Let us see some examples of object. Each key has a value in object.
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```js
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const rectangle = {
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length: 20,
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width: 20
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}
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console.log(rectangle) // {length: 20, width: 20}
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const person = {
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firstName: 'Asabeneh',
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lastName: 'Yetayeh',
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age: 250,
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country: 'Finland',
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city: 'Helsinki',
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skills: [
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'HTML',
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'CSS',
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'JavaScript',
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'React',
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'Node',
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'MongoDB',
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'Python',
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'D3.js'
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],
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isMarried: true
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}
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console.log(person)
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```
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### Getting values from an object
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We can access values of object using two methods:
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- using . followed by key name if the key-name is a one word
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- using square bracket and a quote
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```js
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const person = {
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firstName: 'Asabeneh',
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lastName: 'Yetayeh',
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age: 250,
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country: 'Finland',
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city: 'Helsinki',
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skills: [
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'HTML',
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'CSS',
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'JavaScript',
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'React',
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'Node',
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'MongoDB',
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'Python',
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'D3.js'
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],
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getFullName: function() {
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return `${this.firstName}${this.lastName}`
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},
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'phone number': '+3584545454545'
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}
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// accessing values using .
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console.log(person.firstName)
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console.log(person.lastName)
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console.log(person.age)
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console.log(person.location)
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// value can be accessed using square bracket and key name
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console.log(person['firstName'])
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console.log(person['lastName'])
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console.log(person['age'])
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console.log(person['age'])
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console.log(person['location'])
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// for instance to access the phone number we only use the square bracket method
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console.log(person['phone number'])
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```
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### Creating object methods
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Now, the person object has getFullName properties. The getFullName is function inside the person object and we call it an object method. The _this_ key word refers to the object itself. We can use the word _this_ to access the values of different properties of the object. We can not use an arrow function as object method because the word this refers to the window inside an arrow function instead of the object itself. Example of object:
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```js
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const person = {
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firstName: 'Asabeneh',
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lastName: 'Yetayeh',
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age: 250,
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country: 'Finland',
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city: 'Helsinki',
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skills: [
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'HTML',
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'CSS',
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'JavaScript',
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'React',
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'Node',
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'MongoDB',
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'Python',
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'D3.js'
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],
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getFullName: function() {
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return `${this.firstName} ${this.lastName}`
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}
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}
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console.log(person.getFullName())
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// Asabeneh Yetayeh
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```
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### Setting new key for an object
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An object is a mutable data structure and we can modify the content of an object after it gets created.
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Setting a new keys in an object
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```js
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const person = {
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firstName: 'Asabeneh',
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lastName: 'Yetayeh',
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age: 250,
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country: 'Finland',
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city: 'Helsinki',
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skills: [
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'HTML',
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'CSS',
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'JavaScript',
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'React',
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'Node',
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'MongoDB',
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'Python',
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'D3.js'
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],
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getFullName: function() {
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return `${this.firstName} ${this.lastName}`
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}
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}
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person.nationality = 'Ethiopian'
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person.country = 'Finland'
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person.title = 'teacher'
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person.skills.push('Meteor')
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person.skills.push('SasS')
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person.isMarried = true
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person.getPersonInfo = function() {
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let skillsWithoutLastSkill = this.skills
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.splice(0, this.skills.length - 1)
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.join(', ')
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let lastSkill = this.skills.splice(this.skills.length - 1)[0]
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let skills = `${skillsWithoutLastSkill}, and ${lastSkill}`
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let fullName = this.getFullName()
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let statement = `${fullName} is a ${this.title}.\nHe lives in ${this.country}.\nHe teaches ${skills}.`
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return statement
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}
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console.log(person)
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console.log(person.getPersonInfo())
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```
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```sh
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Asabeneh Yetayeh is a teacher.
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He lives in Finland.
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He teaches HTML, CSS, JavaScript, React, Node, MongoDB, Python, D3.js, Meteor, and SasS.
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```
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### Object Methods
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There are different methods to manipulate an object. Let us see some of the available methods.
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_Object.assign_: To copy an object without modifying the original object
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```js
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const person = {
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name: 'Asabeneh',
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age: 200,
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country: 'Finland',
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skills: ['HTML', 'CSS', 'JS'],
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title: 'teacher',
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address: {
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street: 'Heitamienkatu 16',
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pobox: 2002,
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city: 'Helsinki'
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},
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getPersonInfo: function() {
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return `I am ${this.name} and I live in ${this.country}. I am ${this.age}.`
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}
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}
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//Object methods: Object.assign, Object.keys, Object.values, Object.entries
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//hasOwnProperty
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const copyPerson = Object.assign({}, person)
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console.log(copyPerson)
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```
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#### Getting object keys using Object.keys()
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_Object.keys_: To get the keys or properties of an object as an array
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```js
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const keys = Object.keys(copyPerson)
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console.log(keys) //['name', 'age', 'country', 'skills', 'address', 'getPersonInfo']
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const address = Object.keys(copyPerson.address)
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console.log(address) //['street', 'pobox', 'city']
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```
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#### Getting object values using Object.values()
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_Object.values_:To get values of an object as an array
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```js
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const values = Object.values(copyPerson)
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console.log(values)
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```
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#### Getting object keys and values using Object.entries()
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_Object.entries_:To get the keys and values in an array
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```js
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const entries = Object.entries(copyPerson)
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console.log(entries)
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```
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#### Checking properties using hasOwnProperty()
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_hasOwnProperty_: To check if a specific key or property exist in an object
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```js
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console.log(copyPerson.hasOwnProperty('name'))
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console.log(copyPerson.hasOwnProperty('score'))
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```
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## 💻 Exercises
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1. Create an empty object called dog
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1. Print the the dog object on the console
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1. Add name, legs, color, age and bark properties for the dog object. The bark property is a method which return _woof woof_
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1. Get name, legs, color, age and bark value from the dog object
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1. Set new properties the dog object: breed, getDogInfo
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1. Create an object literal called _personAccount_. It has _firstName, lastName, incomes, expenses_ properties and it has _totalIncome, totalExpense, accountInfo,addIncome, addExpense_ and _accountBalance_ methods. Incomes is a set of incomes and its description and expenses is a set of incomes and its description.
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1. Count logged in users,count users having greater than equal to 50 points from the following object.
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````js
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const users = {
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Alex: {
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email: 'alex@alex.com',
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skills: ['HTML', 'CSS', 'JavaScript'],
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age: 20,
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isLoggedIn: false,
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points: 30
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},
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Asab: {
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email: 'asab@asab.com',
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skills: ['HTML', 'CSS', 'JavaScript', 'Redux', 'MongoDB', 'Express', 'React', 'Node'],
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age: 25,
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isLoggedIn: false,
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points: 50
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},
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Brook: {
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email: 'daniel@daniel.com',
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skills: ['HTML', 'CSS', 'JavaScript', 'React', 'Redux'],
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age: 30,
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isLoggedIn: true,
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points: 50
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},
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Daniel: {
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email: 'daniel@alex.com',
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skills: ['HTML', 'CSS', 'JavaScript', 'Python'],
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age: 20,
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isLoggedIn: false,
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points: 40
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},
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John: {
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email: 'john@john.com',
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skills: ['HTML', 'CSS', 'JavaScript', 'React', 'Redux', 'Node.js'],
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age: 20,
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isLoggedIn: true,
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points: 50
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},
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Thomas: {
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email: 'thomas@thomas.com',
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skills: ['HTML', 'CSS', 'JavaScript', 'React'],
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age: 20,
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isLoggedIn: false,
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points: 40
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},
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Paul: {
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email: 'paul@paul.com',
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skills: ['HTML', 'CSS', 'JavaScript', 'MongoDB', 'Express', 'React', 'Node'],
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age: 20,
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isLoggedIn: false,
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points: 40
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}
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}```
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````
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1. Find people who are MERN stack developer from the users object
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1. Set your name in the users object without modifying the original users object
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1. Get all keys or properties of users object
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1. Get all the values of users object
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1. Use the countries object to print a country name, capital, populations and languages.
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1. \*\*\* Find the 10 most spoken languages:
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````js
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// Your output should look like this
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console.log(mostSpokenLanguages(countries, 10))
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[(91, 'English'),
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(45, 'French'),
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(25, 'Arabic'),
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(24, 'Spanish'),
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(9, 'Russian'),
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(9, 'Portuguese'),
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(8, 'Dutch'),
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(7, 'German'),
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(5, 'Chinese'),
|
||||
(4, 'Swahili'),
|
||||
(4, 'Serbian')]
|
||||
|
||||
// Your output should look like this
|
||||
console.log(mostSpokenLanguages(countries, 3))
|
||||
[
|
||||
(91, 'English'),
|
||||
(45, 'French'),
|
||||
(25, 'Arabic')
|
||||
]```
|
||||
|
||||
````
|
||||
|
||||
1. \*\*\* Use countries_data.js file create a function which create the ten most populated countries
|
||||
|
||||
````js
|
||||
console.log(mostPopulatedCountries(countries, 10))
|
||||
|
||||
[
|
||||
{country: 'China', population: 1377422166},
|
||||
{country: 'India', population: 1295210000},
|
||||
{country: 'United States of America', population: 323947000},
|
||||
{country: 'Indonesia', population: 258705000},
|
||||
{country: 'Brazil', population: 206135893},
|
||||
{country: 'Pakistan', population: 194125062},
|
||||
{country: 'Nigeria', population: 186988000},
|
||||
{country: 'Bangladesh', population: 161006790},
|
||||
{country: 'Russian Federation', population: 146599183},
|
||||
{country: 'Japan', population: 126960000}
|
||||
]
|
||||
|
||||
console.log(mostPopulatedCountries(countries, 3))
|
||||
[
|
||||
{country: 'China', population: 1377422166},
|
||||
{country: 'India', population: 1295210000},
|
||||
{country: 'United States of America', population: 323947000}
|
||||
]```
|
||||
|
||||
````
|
||||
|
||||
1. \*\*\* Try to develop a program which calculate measure of central tendency of a sample(mean, median, mode) and measure of variability(range, variance, standard deviation). In addition to those measures find the min, max, count, percentile, and frequency distribution of the sample. You can create an object called statistics and create all the functions which do statistical calculations as method for the statistics object. Check the output below.
|
||||
|
||||
```js
|
||||
const ages = [31, 26, 34, 37, 27, 26, 32, 32, 26, 27, 27, 24, 32, 33, 27, 25, 26, 38, 37, 31, 34, 24, 33, 29, 26]
|
||||
|
||||
console.log('Count:', statistics.count()) // 25
|
||||
console.log('Sum: ', statistics.sum()) // 744
|
||||
console.log('Min: ', statistics.min()) // 24
|
||||
console.log('Max: ', statistics.max()) // 38
|
||||
console.log('Range: ', statistics.range() // 14
|
||||
console.log('Mean: ', statistics.mean()) // 30
|
||||
console.log('Median: ',statistics.median()) // 29
|
||||
console.log('Mode: ', statistics.mode()) // {'mode': 26, 'count': 5}
|
||||
console.log('Variance: ',statistics.var()) // 17.5
|
||||
console.log('Standard Deviation: ', statistics.std()) // 4.2
|
||||
console.log('Variance: ',statistics.var()) // 17.5
|
||||
console.log('Frequency Distribution: ',statistics.freqDist()) # [(20.0, 26), (16.0, 27), (12.0, 32), (8.0, 37), (8.0, 34), (8.0, 33), (8.0, 31), (8.0, 24), (4.0, 38), (4.0, 29), (4.0, 25)]
|
||||
```
|
||||
|
||||
```sh
|
||||
console.log(statistics.describe())
|
||||
Count: 25
|
||||
Sum: 744
|
||||
Min: 24
|
||||
Max: 38
|
||||
Range: 14
|
||||
Mean: 30
|
||||
Median: 29
|
||||
Mode: (26, 5)
|
||||
Variance: 17.5
|
||||
Standard Deviation: 4.2
|
||||
Frequency Distribution: [(20.0, 26), (16.0, 27), (12.0, 32), (8.0, 37), (8.0, 34), (8.0, 33), (8.0, 31), (8.0, 24), (4.0, 38), (4.0, 29), (4.0, 25)]
|
||||
```
|
||||
|
||||
🎉 CONGRATULATIONS ! 🎉
|
||||
|
||||
[<< Day 7](https://github.com/Asabeneh/30DaysOfJavaScript/blob/master/09_Day/09_day_function_programming.md) | [Day 9 >>](#)
|
||||
File diff suppressed because it is too large
Load Diff
@ -0,0 +1,17 @@
|
||||
<!DOCTYPE html>
|
||||
<html>
|
||||
|
||||
<head>
|
||||
<title>30DaysOfJavaScript:08 Day </title>
|
||||
</head>
|
||||
|
||||
<body>
|
||||
<h1>30DaysOfJavaScript:08 Day</h1>
|
||||
<h2>Objects</h2>
|
||||
|
||||
<script src="./data/countries_obj.js"></script>
|
||||
<script src="./scripts/main.js"></script>
|
||||
|
||||
</body>
|
||||
|
||||
</html>
|
||||
@ -0,0 +1,2 @@
|
||||
console.log(countries)
|
||||
alert('Open the console and check if the countries has been loaded')
|
||||
Loading…
Reference in new issue