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## Table of Contents
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[<< Day 2](https://github.com/Asabeneh/30DaysOfJavaScript/blob/master/02_Day/02_day_data_types.md) | [Day 4 >>](https://github.com/Asabeneh/30DaysOfJavaScript/blob/master/04_Day/04_day_conditionals.md)
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- [📔 Day 3](#%f0%9f%93%94-day-3)
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- [Booleans](#booleans)
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- [Truthy values](#truthy-values)
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- [Falsy values](#falsy-values)
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- [Undefined](#undefined)
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- [Null](#null)
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- [Operators](#operators)
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- [Assignment operators](#assignment-operators)
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- [Arithmetic Operators](#arithmetic-operators)
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- [Comparison Operators](#comparison-operators)
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- [Logical Operators](#logical-operators)
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- [Increment Operator](#increment-operator)
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- [Decrement Operator](#decrement-operator)
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- [Ternary Operators](#ternary-operators)
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- [Operator Precendence](#operator-precendence)
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- [Window Methods](#window-methods)
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- [Window alert() method](#window-alert-method)
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- [Window prompt() method](#window-prompt-method)
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- [Window confirm() method](#window-confirm-method)
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- [Date Object](#date-object)
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- [Creating a time object](#creating-a-time-object)
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- [Getting full year](#getting-full-year)
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- [Getting month](#getting-month)
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- [Getting date](#getting-date)
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- [Getting day](#getting-day)
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- [Getting hours](#getting-hours)
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- [Getting minutes](#getting-minutes)
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- [Getting seconds](#getting-seconds)
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- [Getting time](#getting-time)
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- [💻 Day 3: Exercises](#%f0%9f%92%bb-day-3-exercises)
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- [1. Exercises: Data types Part](#1-exercises-data-types-part)
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- [2. Exercises: Arithmetic Operators Part](#2-exercises-arithmetic-operators-part)
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- [3. Exercises: Booleans Part](#3-exercises-booleans-part)
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- [4. Exercises: Comparison Operators](#4-exercises-comparison-operators)
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- [5. Exercises: Logical Operators](#5-exercises-logical-operators)
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- [6 Ternary Operator](#6-ternary-operator)
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- [7. Exercises: Date time Object](#7-exercises-date-time-object)
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# 📔 Day 3
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## Booleans
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A boolean data type represents one of the two values:_true_ or _false_. Boolean value is either true or false. The use of these data types will be clear when you start the comparison operator. Any comparisons return a boolean value which is either true or false.
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**Example: Boolean Values**
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```js
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let isLightOn = true
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let isRaining = false
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let isHungry = false
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let isMarried = true
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let truValue = 4 > 3 // true
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let falseValue = 3 < 4 // false
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```
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We agreed that boolean values are either true or false.
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### Truthy values
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- All numbers(positive and negative) are truthy except zero
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- All strings are truthy
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- The boolean true
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### Falsy values
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- 0
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- 0n
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- null
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- undefined
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- NaN
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- the boolean false
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- '', "", ``, empty string
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It is good to remember those truthy values and falsy values. In later section, we will use them with conditions to make decision.
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## Undefined
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If we declare a variable and if we do not assign a value, the value will be undefined. In addition to this, if a function is not returning the value will be undefined.
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```js
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let firstName
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console.log(firstName) //not defined, because it is not assigned to a value yet
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```
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## Null
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```js
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let empty = null
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console.log(empty) // -> null , means no value
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```
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## Operators
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### Assignment operators
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An equal sign in JavaScript is an assignment operator. It uses to assign a variable.
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```js
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let firstName = 'Asabeneh'
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let country = 'Finland'
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```
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Assignment Operators
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### Arithmetic Operators
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Arithmetic operators are mathematical operators.
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- Addition(+): a + b
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- Subtraction(-): a - b
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- Multiplication(_): a _ b
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- Division(/): a / b
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- Modulus(%):a % b
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- Exponential(**):a ** b
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```js
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let numOne = 4
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let numTwo = 3
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let sum = numOne + numTwo
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let diff = numOne - numTwo
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let mult = numOne * numTwo
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let div = numOne / numTwo
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let remainder = numOne % numTwo
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let powerOf = numOne ** numTwo
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console.log(sum, diff, mult, div, remainder, powerOf) // 7,1,12,1.33,1, 64
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let PI = 3.14
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let radius = 100 // length in meter
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const gravity = 9.81 // in m/s2
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let mass = 72 // in Kilogram
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const boilingPoint = 100 // temperature in oC, boiling point of water
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const bodyTemp = 37 // body temperature in oC
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//Let us calculate area of a circle
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const areaOfCircle = PI * radius * radius
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console.log(areaOfCircle) // 314 m
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// Let us calculate weight of an object
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const weight = mass * gravity
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console.log(weight) // 706.32 N(Newton)
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//Concatenating string with numbers using string interpolation
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/*
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The boiling point of water is 100 oC.
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Human body temperature is 37 oC.
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The gravity of earth is 9.81 m/s2.
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*/
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console.log(
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`The boiling point of water is ${boilingPoint} oC.\nHuman body temperature is ${bodyTemp} oC.\nThe gravity of earth is ${gravity} m / s2.`
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)
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```
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### Comparison Operators
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In programming we compare values, we use comparison operators to compare two values. We check if a value is greater or less or equal to other value.
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**Example: Comparison Operators**
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```js
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console.log(3 > 2) // true, because 3 is greater than 2
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console.log(3 >= 2) // true, because 3 is greater than 2
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console.log(3 < 2) // false, because 3 is greater than 2
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console.log(2 < 3) // true, because 2 is less than 3
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console.log(2 <= 3) // true, because 2 is less than 3
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console.log(3 == 2) // false, because 3 is not equal to 2
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console.log(3 != 2) // true, because 3 is not equal to 2
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console.log(3 == '3') // true, compare only value
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console.log(3 === '3') // false, compare both value and data type
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console.log(3 !== '3') // true, compare both value and data type
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console.log(3 !== '3') // true, compare both value and data type
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console.log(3 != 3) // false, compare only value
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console.log(3 !== 3) // false, compare both value and data type
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console.log(0 == false) // true, equivalent
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console.log(0 == '') // true, equivalent
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console.log(0 == ' ') // true, equivalent
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console.log(0 === '') // false, not exactly the same
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console.log(0 === false) // false, not exactly the same
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console.log(1 == true) // true, equivalent
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console.log(1 === true) // false, not exactly the same
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console.log(undefined == null) // true
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console.log(undefined === null) // true
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console.log(NaN == NaN) // false, not equal
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console.log(NaN === NaN) // false
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console.log(typeof NaN) // number
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console.log('mango'.length == 'avocado'.length) // false
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console.log('mango'.length != 'avocado'.length) // true
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console.log('mango'.length < 'avocado'.length) // true
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console.log('milk'.length != 'meat'.length) // false
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console.log('milk'.length == 'meat'.length) // true
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console.log('tomato'.length == 'potato'.length) // true
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console.log('python'.length > 'dragon'.length) // false
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```
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Try to understand the above comparisons with some logic. Remember without any logic might be difficult.
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JavaScript is some how a wired kind of programming language. JavaScript code run and give you a result but unless you are good at it may not be the desired result. The following [link](https://dorey.github.io/JavaScript-Equality-Table/) has an exhaustive list of comparison of data types.
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### Logical Operators
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The following symbols are the common logical operators:
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&&(ampersand) , ||(pipe) and !(negation).
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&& gets true only if the two operands are true.
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|| gets true either of the operand is true.
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! negates true to false, false to true.
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```js
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//&& ampersand operator example
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const check = 4 > 3 && 10 > 5 // true and true -> true
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const check = 4 > 3 && 10 < 5 // true and false -> false
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const check = 4 < 3 && 10 < 5 // false and false -> false
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//|| pipe or operator, example
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const check = 4 > 3 || 10 > 5 // true and true -> true
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const check = 4 > 3 || 10 < 5 // true and false -> true
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const check = 4 < 3 || 10 < 5 // false and false -> false
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//! Negation examples
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let check = 4 > 3 // true
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let check = !(4 > 3) // false
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let isLightOn = true
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let isLightOff = !isLightOn // false
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let isMarried = !false // true
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```
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### Increment Operator
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In JavaScrip we use the increment operator to increase a value stored in a variable. The increment could be pre or post increment. Let us see each of them:
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1. Pre-increment
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```js
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let count = 0
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console.log(++count) // 1
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console.log(count) // 1
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```
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1. Post-increment
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```js
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let count = 0
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console.log(count++) // 0
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console.log(count) // 1
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```
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We use most of the time post-increment. At leas you should remember how to use post-increment operator.
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### Decrement Operator
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In JavaScrip we use the decrement operator to decrease a value stored in a variable. The decrement could be pre or post decrement. Let us see each of them:
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1. Pre-decrement
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```js
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let count = 0
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console.log(--count) // -1
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console.log(count) // -1
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```
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2. Post-decrement
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```js
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let count = 0
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console.log(count--) // 0
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console.log(count) // -1
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```
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#### Ternary Operators
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Ternary operator allows to write a condition.
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Another way to write conditionals is using ternary operators. Look at the following examples:
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```js
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let isRaining = true
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isRaining
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? console.log('You need a rain coat.')
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: console.log('No need for a rain coat.')
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isRaining = false
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isRaining
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? console.log('You need a rain coat.')
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: console.log('No need for a rain coat.')
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```
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```sh
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You need a rain coat.
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No need for a rain coat.
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```
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```js
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let number = 5
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number > 0
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? console.log(`${number} is a positive number`)
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: console.log(`${number} is a number number`)
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number = -5
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number > 0
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? console.log(`${number} is a positive number`)
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: console.log(`${number} is a number number`)
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```
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```sh
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5 is a positive number
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-5 is a number number
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```
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### Operator Precendence
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I would like to recommend you to read about operator precendence from this [link](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Operator_Precedence)
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## Window Methods
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### Window alert() method
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As you have seen at very beginning alert() method displays an alert box with a specified message and an OK button. It is a builtin method and it takes on argument.
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```js
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alert(message)
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```
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|
||||
```js
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alert('Welcome to 30DaysOfJavaScript')
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```
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Do not use too much alert because it is destructing and annoying, use it just for to test.
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### Window prompt() method
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The window prompt methods display a prompt box with an input on your browser to take input values and the input data can be stored in a variable. The prompt() method takes two arguments. The second argument is optional.
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```js
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prompt('required text', 'optional text')
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```
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|
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```js
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let number = prompt('Enter number', 'number goes here')
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console.log(number)
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```
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### Window confirm() method
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The confirm() method displays a dialog box with a specified message, along with an OK and a Cancel button.
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A confirm box is often used to ask permission from a user to do something. Window confirm() takes an string as an argument.
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Clicking the OK yields true value, clicking the Cancel button yields false value.
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```js
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const agree = confirm('Are you sure you like to delete? ')
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console.log(agree) // result will be true or false based on what you click on the dialog box
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```
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These are not all the window methods we will have a separate section to go deep into window methods.
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## Date Object
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Time is an important thing. We like to know the time a certain activity or event. In JavaScript current time and date is created using JavaScript Date Object. The object we create using Date object provides many methods to work with date and time.The methods we use to get date and time information from a date object values are started with a word _get_ because it provide the information.
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_getFullYear(), getMonths(), getDate(), getDay(), getHours(), getMinutes, getSeconds(), getMilliseconds(), getTime(), getDay()_
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### Creating a time object
|
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Once we create time object. The time object will provide information about time. Let us create a time object
|
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```js
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const now = new Date()
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console.log(now) // Sat Jan 04 2020 00:56:41 GMT+0200 (Eastern European Standard Time)
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```
|
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|
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We have created a time object and we can access any date time information from the object using the get methods we have mentioned on the table.
|
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|
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### Getting full year
|
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|
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Let's extract or get the full from a time object.
|
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|
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```js
|
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const now = new Date()
|
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console.log(now.getFullYear()) // 2020
|
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```
|
||||
|
||||
### Getting month
|
||||
|
||||
Let's extract or get the month from a time object.
|
||||
|
||||
```js
|
||||
const now = new Date()
|
||||
console.log(now.getMonth()) // 0, because the month is January, month(0-11)
|
||||
```
|
||||
|
||||
### Getting date
|
||||
|
||||
Let's extract or get the date of the month from a time object.
|
||||
|
||||
```js
|
||||
const now = new Date()
|
||||
console.log(now.getDate()) // 4, because the day of the month is 4th, day(0-31)
|
||||
```
|
||||
|
||||
### Getting day
|
||||
|
||||
Let's extract or get the day of the week from a time object.
|
||||
|
||||
```js
|
||||
const now = new Date()
|
||||
console.log(now.getDay()) // 6, because the day is Saturday which is the 5th day,
|
||||
// Getting the weekday as a number (0-6)
|
||||
```
|
||||
|
||||
### Getting hours
|
||||
|
||||
Let's extract or get the hours from a time object.
|
||||
|
||||
```js
|
||||
const now = new Date()
|
||||
console.log(now.getHours()) // 0, because the time is 00:56:41
|
||||
```
|
||||
|
||||
### Getting minutes
|
||||
|
||||
Let's extract or get the minutes from a time object.
|
||||
|
||||
```js
|
||||
const now = new Date()
|
||||
console.log(now.getMinutes()) // 56, because the time is 00:56:41
|
||||
```
|
||||
|
||||
### Getting seconds
|
||||
|
||||
Let's extract or get the seconds from a time object.
|
||||
|
||||
```js
|
||||
const now = new Date()
|
||||
console.log(now.getSeconds()) // 41, because the time is 00:56:41
|
||||
```
|
||||
|
||||
### Getting time
|
||||
|
||||
This method give time in milliseconds starting from January 1, 1970. It is also know as Unix time. We can get the unix time in two ways:
|
||||
|
||||
1. Using _getTime()_
|
||||
|
||||
```js
|
||||
const now = new Date() //
|
||||
console.log(now.getTime()) // 1578092201341, this is the number of seconds passed from January 1, 1970 to January 4, 2020 00:56:41
|
||||
```
|
||||
|
||||
1. Using _Date.now()_
|
||||
|
||||
```js
|
||||
const allSeconds = Date.now() //
|
||||
console.log(allSeconds) // 1578092201341, this is the number of seconds passed from January 1, 1970 to January 4, 2020 00:56:41
|
||||
const timeInSeconds = new Date().getTime()
|
||||
console.log(allSeconds == timeInSeconds) // true
|
||||
```
|
||||
|
||||
Let us format these values to a human readable time format.
|
||||
**Example:**
|
||||
|
||||
```js
|
||||
const now = new Date()
|
||||
const year = now.getFullYear() // return year
|
||||
const month = now.getMonth() + 1 // return month(0 - 11)
|
||||
const date = now.getDate() // return date (1 - 31)
|
||||
const hours = now.getHours() // return number (0 - 23)
|
||||
const minutes = now.getMinutes() // return number (0 -59)
|
||||
console.log(`${date}/${month}/${year} ${hours}:${minutes}`) // 4/1/2020 0:56
|
||||
```
|
||||
|
||||
🌕 You have boundless energy. You have just completed day 3 challenge and you are three steps a head in to your way to greatness. Now do some exercises for your brain and for your muscle.
|
||||
|
||||
# 💻 Day 3: Exercises
|
||||
|
||||
## 1. Exercises: Data types Part
|
||||
|
||||
1. Declare firstName, lastName, country, city, age, isMarried, year variable and assign value to it
|
||||
1. The JavaScript typeof operator uses to check different data types. Check the data type of each variables from question number 1.
|
||||
1. Check if type of '10' is equal to 10
|
||||
1. Check if parseInt('9.8') is equal to 10
|
||||
|
||||
## 2. Exercises: Arithmetic Operators Part
|
||||
|
||||
1. Write a script that prompt the user to enter base and height of the triangle and calculate an area of a triangle (area = 0.5 x b x h).
|
||||
|
||||
```sh
|
||||
Enter base: 20
|
||||
Enter height: 10
|
||||
The area of the triangle is 50
|
||||
```
|
||||
|
||||
1. Write a script that prompt the user to enter side a, side b, and side c of the triangle and and calculate the perimeter of triangle (perimeter = a + b + c)
|
||||
|
||||
```sh
|
||||
Enter side a: 5
|
||||
Enter side b: 4
|
||||
Enter side c: 3
|
||||
The perimeter of the triangle is 12
|
||||
```
|
||||
|
||||
1. Get length and width using prompt and calculate an area of rectangle (area = length x width and the perimeter of rectangle (perimeter = 2 x (length + width))
|
||||
1. Get radius using prompt and calculate the area of a circle (area = pi x r x r) and circumference of a circle(c = 2 x pi x r) where pi = 3.14.
|
||||
1. Calculate the slope, x-intercept and y-intercept of y = 2x -2
|
||||
1. Slope is (m = y2-y1/x2-x1). Find the slope between point (2, 2) and point(6,10)
|
||||
1. Compare the slope of above two questions.
|
||||
1. Calculate the value of y (y = x^2 + 6x + 9). Try to use different x values and figure out at what x value y is 0.
|
||||
1. Writ a script that prompt a user to enters hours and rate per hour. Calculate pay of the person?
|
||||
|
||||
```sh
|
||||
Enter hours: 40
|
||||
Enter rate per hour: 28
|
||||
Your weekly earning is 1120
|
||||
```
|
||||
|
||||
1. Write a script that prompt the user to enter number of years. Calculate the number of seconds a person can live. Assume some one lives just hundred years
|
||||
|
||||
```sh
|
||||
Enter number of yours you live: 100
|
||||
You lived 3153600000 seconds.
|
||||
```
|
||||
|
||||
## 3. Exercises: Booleans Part
|
||||
|
||||
Boolean value is either true or false.
|
||||
|
||||
1. Write three JavaScript statement which provide truthy value.
|
||||
1. Write three JavaScript statement which provide falsy value.
|
||||
|
||||
## 4. Exercises: Comparison Operators
|
||||
|
||||
Figure out the result of the following comparison expression first without using console.log(). After you decide the result confirm it using console.log()
|
||||
|
||||
1. 4 > 3
|
||||
1. 4 >= 3
|
||||
1. 4 < 3
|
||||
1. 4 <= 3
|
||||
1. 4 == 4
|
||||
1. 4 === 4
|
||||
1. 4 != 4
|
||||
1. 4 !== 4
|
||||
1. 4 != '4'
|
||||
1. 4 == '4'
|
||||
1. 4 === '4'
|
||||
Find the length of python and jargon and make a falsy comparison statement.
|
||||
|
||||
## 5. Exercises: Logical Operators
|
||||
|
||||
1. Figure out the result of the following expressions first without using console.log(). After you decide the result confirm it by using console.log()
|
||||
1. 4 > 3 && 10 < 12
|
||||
2. 4 > 3 && 10 > 12
|
||||
3. 4 > 3 || 10 < 12
|
||||
4. 4 > 3 || 10 > 12
|
||||
5. !(4 > 3)
|
||||
6. !(4 < 3)
|
||||
7. !(false)
|
||||
8. !(4 > 3 && 10 < 12)
|
||||
9. !(4 > 3 && 10 > 12)
|
||||
10. !(4 === '4')
|
||||
2. There is no 'on' in both dragon and python
|
||||
|
||||
## 6 Ternary Operator
|
||||
|
||||
1. If the length of your name is greater than 7 say, your name is long else say your name is short.
|
||||
1. Compare your first name length and your family name length and you should get this output.
|
||||
|
||||
```js
|
||||
let firstName = 'Asabeneh'
|
||||
let lastName = 'Yetayeh'
|
||||
```
|
||||
|
||||
```sh
|
||||
//Output
|
||||
Your first name, Asabeneh is longer than your family name, Yetayeh
|
||||
```
|
||||
|
||||
1. Declare two variables _myAge_ and _yourAge_ and assign them initial values and myAge and yourAge.
|
||||
Output:
|
||||
|
||||
```js
|
||||
let myAge = 250
|
||||
let yourAge = 25
|
||||
```
|
||||
|
||||
```sh
|
||||
//output
|
||||
I am 225 years older than you.
|
||||
```
|
||||
|
||||
1. Using prompt get the year the user was born and if the user is 18 or above allow the user to drive if not tell the user to wait a certain amount of years.
|
||||
|
||||
```sh
|
||||
// if the age is 25
|
||||
You are 25. You are old enough to drive
|
||||
// if the age is under 18
|
||||
You are 15. You will be allowed to drive after 3 years.
|
||||
```
|
||||
|
||||
## 7. Exercises: Date time Object
|
||||
|
||||
1. What is the year today?
|
||||
1. What is the month today as a number?
|
||||
1. What is the date today?
|
||||
1. What is the day today as a number?
|
||||
1. What is the hours now?
|
||||
1. What is the minutes now?
|
||||
1. Find out the numbers of seconds elapsed from January 1, 1970 to now.
|
||||
1. Create a human readable time format
|
||||
1. YYY-MM-DD HH:mm:ss
|
||||
2. DD-MM-YYYY HH:mm:ss
|
||||
3. DD/MM/YYY HH:mm:ss
|
||||
|
||||
🎉 CONGRATULATIONS ! 🎉
|
||||
|
||||
[<< Day 2](https://github.com/Asabeneh/30DaysOfJavaScript/blob/master/02_Day/02_day_data_types.md) | [Day 4 >>](https://github.com/Asabeneh/30DaysOfJavaScript/blob/master/04_Day/04_day_conditionals.md)
|
||||
|
After Width: | Height: | Size: 76 KiB |
@ -0,0 +1,312 @@
|
||||
## Table of Contents
|
||||
|
||||
[<< Day 3](https://github.com/Asabeneh/30DaysOfJavaScript/blob/master/03_Day/03_day_booleans_operators_date.md) | [Day 5 >>](#)
|
||||
--
|
||||
|
||||
|
||||
|
||||
- [📔 Day 4](#%f0%9f%93%94-day-4)
|
||||
- [Conditionals](#conditionals)
|
||||
- [If](#if)
|
||||
- [If Else](#if-else)
|
||||
- [If else if else](#if-else-if-else)
|
||||
- [Switch](#switch)
|
||||
- [Ternary Operators](#ternary-operators)
|
||||
- [💻 Exercise - 8 : Conditionals](#%f0%9f%92%bb-exercise---8--conditionals)
|
||||
|
||||
# 📔 Day 4
|
||||
|
||||
## Conditionals
|
||||
|
||||
Conditional statements are used to decision based on different conditions.
|
||||
By default , statements in JavaScript script executed sequentially from top to bottom. If the processing logic require so, the sequential flow of execution can be altered in two ways:
|
||||
|
||||
- Conditional execution: a block of one or more statements will be executed if a certain expression is true
|
||||
- Repetitive execution: a block of one or more statements will be repetitively executed as long as a certain expression is true. In this section, we will cover _if_, _else_ , _else if_ statements. The comparison and logical operator we learned in the previous sections will be useful in here.
|
||||
|
||||
Conditions can be implementing using the following ways:
|
||||
|
||||
- if
|
||||
- if else
|
||||
- if else if else
|
||||
- switch
|
||||
- ternary operator
|
||||
|
||||
### If
|
||||
|
||||
In JavaScript and other programming languages the key word _if_ use to check if a condition is true and to execute the block code. To create an if condition, we need _if_ keyword, condition inside a parenthesis and block of code inside a curly bracket({}).
|
||||
|
||||
```js
|
||||
// syntax
|
||||
if (condition) {
|
||||
//this part of code run for truthy condition
|
||||
}
|
||||
```
|
||||
|
||||
**Example:**
|
||||
|
||||
```js
|
||||
let num = 3
|
||||
if (num > 0) {
|
||||
console.log(`${num} is a positive number`)
|
||||
}
|
||||
// 3 is a positive number
|
||||
```
|
||||
|
||||
```js
|
||||
let isRaining = true
|
||||
if (isRaining) {
|
||||
console.log('Remember to take your rain coat.')
|
||||
}
|
||||
```
|
||||
|
||||
As you can see in the above condition, 3 is greater than 0 and it is a positive number. The condition was true and the block code was executed. However, if the condition is false, we do not see a result. The same goes for the second condition, if isRaining is false the if block will not be executed and we do not see an output. In order to see the result of the falsy condition, we should have another block, which is going to be _else_.
|
||||
|
||||
### If Else
|
||||
|
||||
If condition is true the first block will be executed, if not the else condition will be executed.
|
||||
|
||||
```js
|
||||
// syntax
|
||||
if (condition) {
|
||||
// this part of code run for truthy condition
|
||||
} else {
|
||||
// this part of code run for false condition
|
||||
}
|
||||
```
|
||||
|
||||
```js
|
||||
let num = 3
|
||||
if (num > 0) {
|
||||
console.log(`${num} is a positive number`)
|
||||
} else {
|
||||
console.log(`${num} is a negative number`)
|
||||
}
|
||||
// 3 is a positive number
|
||||
|
||||
num = -3
|
||||
if (num > 0) {
|
||||
console.log(`${num} is a positive number`)
|
||||
} else {
|
||||
console.log(`${num} is a negative number`)
|
||||
}
|
||||
// -3 is a negative number
|
||||
```
|
||||
|
||||
```js
|
||||
let isRaining = true
|
||||
if (isRaining) {
|
||||
console.log('You need a rain coat.')
|
||||
} else {
|
||||
console.log('No need for a rain coat.')
|
||||
}
|
||||
// You need a rain coat.
|
||||
|
||||
isRaining = false
|
||||
if (isRaining) {
|
||||
console.log('You need a rain coat.')
|
||||
} else {
|
||||
console.log('No need for a rain coat.')
|
||||
}
|
||||
// No need for a rain coat.
|
||||
```
|
||||
|
||||
The above condition is false, therefore the else block was executed. How about if our condition is more than two, we will use *ele if* conditions.
|
||||
|
||||
### If else if else
|
||||
|
||||
On our daily life, we make decision on daily basis. We make decision not by checking one or two conditions instead we make decisions based on multiple conditions. As similar to our daily life, programming is also full conditions. We use *else if* when we have multiple conditions.
|
||||
|
||||
```js
|
||||
// syntax
|
||||
if (condition) {
|
||||
// code
|
||||
} else if (condition) {
|
||||
// code
|
||||
} else {
|
||||
// code
|
||||
|
||||
}
|
||||
```
|
||||
|
||||
**Example:**
|
||||
|
||||
```js
|
||||
let a = 0
|
||||
if (a > 0) {
|
||||
console.log(`A${a} is a positive number`)
|
||||
} else if (a < 0) {
|
||||
print(`${a} is a negative number`)
|
||||
else if (a == 0) {
|
||||
print(` ${a} is zero`)
|
||||
} else {
|
||||
print('${a) is not a number')
|
||||
}
|
||||
```
|
||||
|
||||
```js
|
||||
// if else if else
|
||||
let weather = 'sunny'
|
||||
if (weather === 'rainy') {
|
||||
console.log('You need a rain coat.')
|
||||
} else if (weather === 'cloudy') {
|
||||
console.log('It might be cold, you need a jacket.')
|
||||
} else if (weather === 'sunny') {
|
||||
console.log('Go out freely.')
|
||||
} else {
|
||||
console.log('No need for rain coat.')
|
||||
}
|
||||
```
|
||||
|
||||
### Switch
|
||||
|
||||
Switch is an alternative for **if else if else else**
|
||||
|
||||
```js
|
||||
let weather = 'cloudy'
|
||||
switch (weather) {
|
||||
case 'rainy':
|
||||
console.log('You need a rain coat.')
|
||||
break
|
||||
case 'cloudy':
|
||||
console.log('It might be cold, you need a jacket.')
|
||||
break
|
||||
case 'sunny':
|
||||
console.log('Go out freely.')
|
||||
break
|
||||
default:
|
||||
console.log(' No need for rain coat.')
|
||||
}
|
||||
// Switch More Examples
|
||||
var dayUserInput = prompt('What day is today ?')
|
||||
var day = dayUserInput.toLowerCase()
|
||||
switch (day) {
|
||||
case 'monday':
|
||||
console.log('Today is Monday')
|
||||
break
|
||||
case 'tuesday':
|
||||
console.log('Today is Tuesday')
|
||||
break
|
||||
case 'wednesday':
|
||||
console.log('Today is Wednesday')
|
||||
break
|
||||
case 'thursday':
|
||||
console.log('Today is Thursday')
|
||||
break
|
||||
case 'friday':
|
||||
console.log('Today is Friday')
|
||||
break
|
||||
case 'saturday':
|
||||
console.log('Today is Saturday')
|
||||
break
|
||||
case 'sunday':
|
||||
console.log('Today is Sunday')
|
||||
break
|
||||
|
||||
default:
|
||||
console.log('It is not a week day.')
|
||||
}
|
||||
```
|
||||
|
||||
### Ternary Operators
|
||||
|
||||
Another way to write conditionals is using ternary operators. We have covered this in other sections but we should also mention it here.
|
||||
|
||||
```js
|
||||
let isRaining = true
|
||||
isRaining
|
||||
? console.log('You need a rain coat.')
|
||||
: console.log('No need for a rain coat.')
|
||||
```
|
||||
|
||||
🌕 You are extraordinary and you have a remarkable potential. You have just completed day 4 challenge and you are four steps a head in to your way to greatness. Now do some exercises for your brain and for your muscle.
|
||||
|
||||
# 💻 Exercise - 8 : Conditionals
|
||||
|
||||
1. Get user input using prompt(“Enter your age:”). If user is 18 or older , give feedback:You are old enough to drive but if not 18 give feedback to wait for the years he supposed to wait for.
|
||||
|
||||
```sh
|
||||
Enter your age: 30
|
||||
You are old enough to drive.
|
||||
|
||||
Enter your age:15
|
||||
You are left with 3 years to drive.
|
||||
```
|
||||
|
||||
1. Compare the values of myAge and yourAge using if … else. Based on the comparison log to console who is older (me or you). Use prompt(“Enter your age:”) to get the age as input.
|
||||
|
||||
```sh
|
||||
Enter your age: 30
|
||||
You are 5 years older than me.
|
||||
```
|
||||
|
||||
1. If a is greater than b return a is greater than b else a is less than b. Do it both using if else and ternary operator.
|
||||
|
||||
```js
|
||||
let a = 4
|
||||
let b = 3
|
||||
```
|
||||
|
||||
```sh
|
||||
4 is greater than 3
|
||||
```
|
||||
|
||||
1. Write a code which give grade students according to theirs scores:
|
||||
- 80-100, A
|
||||
- 70-89, B
|
||||
- 60-69, C
|
||||
- 50-59, D
|
||||
- 0 -49, F
|
||||
1. Check if the season is Autumn, Winter, Spring or Summer.
|
||||
If the user input is:
|
||||
- September, October or November, the season is Autumn.
|
||||
- December, January or February, the season is Winter.
|
||||
- March, April or May, the season is Spring
|
||||
- June, July or August, the season is Summer
|
||||
|
||||
1. Even numbers are divisible by 2 and the remainder is zero. How do you check if a number is even or not using JavaScript?
|
||||
|
||||
```sh
|
||||
Enter a number: 2
|
||||
2 is an even number
|
||||
|
||||
Enter a number 9
|
||||
9 is is an odd number.
|
||||
```
|
||||
|
||||
1. Check if a day is week end day or a working day. Your script will take day as an input.
|
||||
|
||||
```sh
|
||||
What is the day is today? Saturday
|
||||
Saturday is a weekend day.
|
||||
|
||||
What is the day today? saturDaY
|
||||
Saturday is a weekend day.
|
||||
|
||||
What is the day today? Friday
|
||||
Friday is a work day.
|
||||
|
||||
What is the day today? FrIDAy
|
||||
Friday is a work day.
|
||||
```
|
||||
|
||||
8. Write a program which tells the number days in a month.
|
||||
|
||||
```sh
|
||||
Enter month: January
|
||||
January has 31 days.
|
||||
|
||||
Enter month: JANUARY
|
||||
January has 31 day
|
||||
|
||||
Enter month: February
|
||||
February has 28 days.
|
||||
|
||||
Enter month: FEbruary
|
||||
February has 28 days.
|
||||
```
|
||||
|
||||
|
||||
🎉 CONGRATULATIONS ! 🎉
|
||||
|
||||
[<< Day 3](https://github.com/Asabeneh/30DaysOfJavaScript/blob/master/03_Day/03_day_booleans_operators_date.md) | [Day 5 >>](#)
|
||||
|
After Width: | Height: | Size: 75 KiB |
|
After Width: | Height: | Size: 81 KiB |
|
After Width: | Height: | Size: 74 KiB |
Loading…
Reference in new issue