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30-Days-Of-JavaScript
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03_Day/03_booleans_operators_date.md
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@ -17,7 +17,7 @@
![Thirty Days Of JavaScript](../images/banners/day_1_3.png)
- [📔 Day 3](#%f0%9f%93%94-day-3)
- [📔 Day 3](#-day-3)
- [Booleans](#booleans)
- [Truthy values](#truthy-values)
- [Falsy values](#falsy-values)
@ -46,7 +46,7 @@
- [Getting minutes](#getting-minutes)
- [Getting seconds](#getting-seconds)
- [Getting time](#getting-time)
- [💻 Day 3: Exercises](#%f0%9f%92%bb-day-3-exercises)
- [💻 Day 3: Exercises](#-day-3-exercises)
- [Exercises: Level 1](#exercises-level-1)
- [Exercises: Level 2](#exercises-level-2)
- [Exercises: Level 3](#exercises-level-3)
@ -86,11 +86,11 @@ We agreed that boolean values are either true or false.
- the boolean false
- '', "", ``, empty string
It is good to remember those truthy values and falsy values. In later section, we will use them with conditions to make decision.
It is good to remember those truthy values and falsy values. In later section, we will use them with conditions to make decisions.
## Undefined
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.
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, it will be undefined.
```js
let firstName
@ -145,23 +145,26 @@ console.log(sum, diff, mult, div, remainder, powerOf) // 7,1,12,1.33,1, 64
```
```js
let PI = 3.14
const PI = 3.14
let radius = 100 // length in meter
const gravity = 9.81 // in m/s2
let mass = 72 // in Kilogram
const boilingPoint = 100 // temperature in oC, boiling point of water
const bodyTemp = 37 // body temperature in oC
//Let us calculate area of a circle
const areaOfCircle = PI * radius * radius
console.log(areaOfCircle) // 314 m
const gravity = 9.81 // in m/s2
let mass = 72 // in Kilogram
// Let us calculate weight of an object
const weight = mass * gravity
console.log(weight) // 706.32 N(Newton)
//Concatenating string with numbers using string interpolation
const boilingPoint = 100 // temperature in oC, boiling point of water
const bodyTemp = 37 // body temperature in oC
// Concatenating string with numbers using string interpolation
/*
The boiling point of water is 100 oC.
Human body temperature is 37 oC.
@ -190,14 +193,13 @@ console.log(3 != 2) // true, because 3 is not equal to 2
console.log(3 == '3') // true, compare only value
console.log(3 === '3') // false, compare both value and data type
console.log(3 !== '3') // true, compare both value and data type
console.log(3 !== '3') // true, compare both value and data type
console.log(3 != 3) // false, compare only value
console.log(3 !== 3) // false, compare both value and data type
console.log(0 == false) // true, equivalent
console.log(0 === false) // false, not exactly the same
console.log(0 == '') // true, equivalent
console.log(0 == ' ') // true, equivalent
console.log(0 === '') // false, not exactly the same
console.log(0 === false) // false, not exactly the same
console.log(1 == true) // true, equivalent
console.log(1 === true) // false, not exactly the same
console.log(undefined == null) // true
@ -209,13 +211,13 @@ console.log(typeof NaN) // number
console.log('mango'.length == 'avocado'.length) // false
console.log('mango'.length != 'avocado'.length) // true
console.log('mango'.length < 'avocado'.length) // true
console.log('milk'.length != 'meat'.length) // false
console.log('milk'.length == 'meat'.length) // true
console.log('milk'.length != 'meat'.length) // false
console.log('tomato'.length == 'potato'.length) // true
console.log('python'.length > 'dragon'.length) // false
```
Try to understand the above comparisons with some logic. Remember without any logic might be difficult.
Try to understand the above comparisons with some logic. Remembering without any logic might be difficult.
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.
As rule of thumb, if a value is not true with == it will not be equal with ===. Using === is safer than using ==. The following [link](https://dorey.github.io/JavaScript-Equality-Table/) has an exhaustive list of comparison of data types.
@ -224,30 +226,30 @@ As rule of thumb, if a value is not true with == it will not be equal with ===.
The following symbols are the common logical operators:
&&(ampersand) , ||(pipe) and !(negation).
&& gets true only if the two operands are true.
|| gets true either of the operand is true.
! negates true to false, false to true.
The && operator gets true only if the two operands are true.
The || operator gets true either of the operand is true.
The ! operator negates true to false and false to true.
```js
//&& ampersand operator example
// && ampersand operator example
const check = 4 > 3 && 10 > 5 // true && true -> true
const check = 4 > 3 && 10 < 5 // true && false -> false
const check = 4 < 3 && 10 < 5 // false && false -> false
const check = 4 > 3 && 10 > 5 // true && true -> true
const check = 4 > 3 && 10 < 5 // true && false -> false
const check = 4 < 3 && 10 < 5 // false && false -> false
//|| pipe or operator, example
// || pipe or operator, example
const check = 4 > 3 || 10 > 5 // true || true -> true
const check = 4 > 3 || 10 < 5 // true || false -> true
const check = 4 < 3 || 10 < 5 // false || false -> false
const check = 4 > 3 || 10 > 5 // true || true -> true
const check = 4 > 3 || 10 < 5 // true || false -> true
const check = 4 < 3 || 10 < 5 // false || false -> false
//! Negation examples
let check = 4 > 3 // true
let check = !(4 > 3) // false
let check = 4 > 3 // true
let check = !(4 > 3) // false
let isLightOn = true
let isLightOff = !isLightOn // false
let isMarried = !false // true
let isLightOff = !isLightOn // false
let isMarried = !false // true
```
### Increment Operator
@ -258,16 +260,16 @@ In JavaScrip we use the increment operator to increase a value stored in a varia
```js
let count = 0
console.log(++count) // 1
console.log(count) // 1
console.log(++count) // 1
console.log(count) // 1
```
1. Post-increment
```js
let count = 0
console.log(count++) // 0
console.log(count) // 1
console.log(count++) // 0
console.log(count) // 1
```
We use most of the time post-increment. At leas you should remember how to use post-increment operator.
@ -349,7 +351,7 @@ alert(message)
alert('Welcome to 30DaysOfJavaScript')
```
Do not use too much alert because it is destructing and annoying, use it just for to test.
Do not use too much alert because it is destructing and annoying, use it just to test.
### Window prompt() method
@ -367,8 +369,8 @@ console.log(number)
### Window confirm() method
The confirm() method displays a dialog box with a specified message, along with an OK and a Cancel button.
A confirm box is often used to ask permission from a user to do something. Window confirm() takes an string as an argument.
Clicking the OK yields true value, clicking the Cancel button yields false value.
A confirm box is often used to ask permission from a user to execute something. Window confirm() takes a string as an argument.
Clicking the OK yields true value, whereas clicking the Cancel button yields false value.
```js
const agree = confirm('Are you sure you like to delete? ')
@ -397,7 +399,7 @@ We have created a time object and we can access any date time information from t
### Getting full year
Let's extract or get the full from a time object.
Let's extract or get the full year from a time object.
```js
const now = new Date()
@ -419,7 +421,7 @@ 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)
console.log(now.getDate()) // 4, because the day of the month is 4th, day(1-31)
```
### Getting day
@ -428,7 +430,8 @@ 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,
console.log(now.getDay()) // 6, because the day is Saturday which is the 7th day
// Sunday is 0, Monday is 1 and Saturday is 6
// Getting the weekday as a number (0-6)
```
@ -494,7 +497,7 @@ 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 challenges and you are three steps a head in to your way to greatness. Now do some exercises for your brain and for your muscle.
🌕 You have boundless energy. You have just completed day 3 challenges 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
@ -618,13 +621,13 @@ console.log(`${date}/${month}/${year} ${hours}:${minutes}`) // 4/1/2020 0:56
```
1. Create a human readable time format using the Date time object
1. YYY-MM-DD HH:mm
1. YYYY-MM-DD HH:mm
2. DD-MM-YYYY HH:mm
3. DD/MM/YYY HH:mm
3. DD/MM/YYYY HH:mm
### Exercises: Level 3
1. Create a human readable time format using the Date time object. The hour and the minute should be all time two digits(7 hours should be 07 and 5 minutes should be 05 )
1. Create a human readable time format using the Date time object. The hour and the minute should be all the time two digits(7 hours should be 07 and 5 minutes should be 05 )
1. YYY-MM-DD HH:mm eg. 20120-01-02 07:05
🎉 CONGRATULATIONS ! 🎉

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