The JavaScript Math Object has a random() method number generator which generators number from 0 to 0.999999999...
```js
let randomNum = Math.random() // generates 0 to 0.999
```
Now, let us see how we can use random() method to generate a random number between 0 and 10 inclusive.
```js
let randomNum = Math.random() // generates 0 to 0.999
let numBtnZeroAndTen = randomNum * 11
console.log(numBtnZeroAndTen) // this gives: min 0 and max 10.99
let randomNumRoundToFloor = Math.floor(numBtnZeroAndTen)
console.log(randomNumRoundToFloor) // this gives between 0 and 10
```
## Strings
Strings are texts, which are under **_single_** or **_double_** quote. To declare a string, we need a variable name, assignment operator, a value under a single quote, double-quote, or backtick.
let age = 250 // int, it is not my real age, do not worry about it
console.log(typeof 'Asabeneh') // str
console.log(typeof firstName) // str
console.log(typeof 10) // number
console.log(typeof 3.14) // number
console.log(typeof true) // bool
```
### Math Object
### Changing data type(Casting)
In JavaScript the Math Object provides a lots of methods to work with numbers.
- Casting: Converting one data type to another data type. We use _parseInt()_, _parsefloat()_,_Number()_, _+ sign_, _str()_
When we do arithmetic operations string numbers should be first converted to integer or float if not it returns an error.
```js
const PI = Math.PI
console.log(PI) // 3.141592653589793
console.log(Math.round(PI)) // 3; to round values to the nearest number
console.log(Math.round(9.81)) // 10
console.log(Math.floor(PI)) // 3; rounding down
console.log(Math.ceil(PI)) // 4; rounding up
console.log(Math.min(-5, 3, 20, 4,5, 10)) // -5, returns the minimum value
console.log(Math.max(-5, 3, 20, 4,5, 10)) // 20, returns the maximum value
#### String to Int
const randNum = Math.random() // creates random number between 0 to 0.999999
console.log(randNum)
// Let create random number between 0 to 10
const num = Math.floor(Math.random () * 11) // creates random number between 0 and 10
console.log(num)
We can convert string number to a number. Any number inside a quote is a string number. An example of a string number: '10', '5', etc.
We can convert string to number using the following methods:
//Absolute value
console.log(Math.abs(-10)) //10
//Square root
console.log(Math.sqrt(100)) // 10
console.log(Math.sqrt(2)) //1.4142135623730951
// Power
console.log(Math.pow(3, 2)) // 9
console.log(Math.E) // 2.718
- parseInt()
- Number()
- +
// Logarithm
//Returns the natural logarithm of base E of x, Math.log(x)
console.log(Math.log(2)) // 0.6931471805599453
console.log(Math.log(10)) // 2.302585092994046
```js
let num = '10'
let numInt = parseInt(num)
console.log(numInt) // 10
```
// Trigonometry
Math.sin(0)
Math.sin(60)
```js
let num = '10'
let numInt = Number(num)
console.log(numInt) // 10
```
Math.cos(0)
Math.cos(60)
```js
let num = '10'
let numInt = +num
console.log(numInt) // 10
```
#### Random number generator
#### String to Float
The JavaScript Math Object has a random() method number generator which generators number from 0 to 0.999999999...
We can convert string float number to a float number. Any float number inside a quote is a string float number. An example of a string float number: '9.81', '3.14', '1.44', etc.
We can convert string float to number using the following methods:
- parseFloat()
- Number()
- +
```js
let randomNum = Math.random() // generates 0 to 0.999
let num = '9.81'
let numFloat = parseFloat(num)
console.log(numFloat) // 9.81
```
Now, let us see how we can use random() method to generate a random number between 0 and 10 inclusive.
```js
let num = '9.81'
let numFloat = Number(num)
console.log(numFloat) // 9.81
```
```js
let randomNum = Math.random() // generates 0 to 0.999
let numBtnZeroAndTen = randomNum * 11
console.log(numBtnZeroAndTen) // this gives: min 0 and max 10.99
let randomNumRoundToFloor = Math.floor(numBtnZeroAndTen)
console.log(randomNumRoundToFloor) // this gives between 0 and 10
let num = '9.81'
let numFloat = +num
console.log(numInt) // 9.81
```
#### Float to Int
We can convert float numbers to integers.
We use the following method to convert float to int:
- parseInt()
```js
let num = 9.81
let numInt = parseInt(num)
console.log(numInt) // 9
```
🌕 You are awesome. You have just completed day 2 challenge and you are two steps a head in to your way to greatness. Now do some exercises for your brain and for your muscle.
# 💻 Day 2: Exercises
## Exercises: String Part
1. Declare a variable name challenge and assign it to an initial value **'30 Days Of JavaScript'**.
2. Print the string on the browser console using __console.log()__
3. Print the __length__ of the string on the browser console using _console.log()_
@ -789,7 +824,6 @@ The quote 'There is no exercise better for the heart than reaching down and lift
"Love is not patronizing and charity isn't about pity, it is about love. Charity and love are the same -- with charity you give love, so don't just give money but reach out your hand instead."
```
32.
33. Check if 'on' is found in both python and jargon
34. _I hope this course is not full of jargon_. Check if _jargon_ is in the sentence.
35. Generate a random number between 0 and 100 inclusive.
@ -798,13 +832,16 @@ The quote 'There is no exercise better for the heart than reaching down and lift
38. Access the 'JavaScript' string characters using a random number.
39. Use console.log() and escape characters to print the following pattern.
```js
1 1 1 1 1
2 1 2 4 8
3 1 3 9 27
4 1 4 16 64
5 1 5 25 125
```
```js
1 1 1 1 1
2 1 2 4 8
3 1 3 9 27
4 1 4 16 64
5 1 5 25 125
```
40. Check if typeof '10' is exactly equal to 10. If not make it exactly equal.
20. Check if parseInt('9.8') is equal to 10 if not make it exactly equal with 10.
Asabeneh
6 years ago