All language subtitles for 9- Bitwise Opertors

Finally, the

last group of operators we're going to look at is bitwise operators.

Now, this really requires me to go beyond the

scope of this course, I have to talk about some computer science stuff, and honestly

I don't really want to bore you, because this stuff doesn't really have that much

practical usage in the real world, I'm not saying their useless,

they definitely have their own use, but they are more on the theoretical

side and it's not something that you will use on a daily basis. However,

if you're really enthusiastic, I'm going to explain what

bitwise operators are, and how they work, but feel free to skip this lecture if you just want

to focus on the practicality. So you know that we

humans use the decimal system to represent numbers. So 1

2345. But in computers, these numbers are stored

in the binary format, which is a combination of 0's

and 1's. So let's take a look at a few examples. The

number 1 in the decimal system, is represented as 7

0's, 1234567, and 1.

So we have 8 digits, each digit is what we call

a bit, so here we have 8 bits, which represents

1 byte of information in a computer. Here's another

example. Number 2 in the decimal system equals to

there are six 0's and then 1, 0.

There are mathematical formulas behind this, for converting numbers between decimal

and binary systems, if you don't want to learn the mathematics, you can simply

Google decimal to binary converter. Now,

bitwise operators in JavaScript or any other programming languages, are

similar to logical operators, but they work in the individual

bits of a number. Let me show you what I mean by this.

So, I'm going to do a console.log, 1

or 2. Note that here we have a single

vertical line, that represents a bit wise or,

bitwise OR, logical or's

have double vertical lines. So when we apply the bitwise or

between 1 and 2, this is what's going to happen. So,

I add r as the result here. Now,

this operators is going to look at each of these beats like this,

in a vertical way, if either of these bits is one, the result

will be 1, otherwise it will be 0. So here, in both

these numbers, the first 6 bits are 0, so,

in the result you also have 6 0's. Now

the 7 bit will be 1, because here we have

1 at this position, right? And similarly, the 8 bit

will be 1, because here we have a 1. Now if we

convert this binary number to a decimal number the result will be

3. So let's save the changes

and you can see on the console we have 3.

Bitwise and a similar. So let's duplicate this, bitwise, and

will use a single ampersand for that.

ing 0, now the result is going to be something like this. So, if

both numbers are 1, 1 will be returned otherwise

will be 0. So in this case all the bits will end up

being 0, because if you look if you look at these two first numbers, 1 and 2,

their first 6 bits are 0,

and here in the second number we have this bit that is 1,

but the bit at the equivalent position here is 0. So if we apply

it with and between these two bits the results will be 0, okay?

So, this binary number equals 0 in the

decimal system. But save the changes, and see this on the console.

Save, here it is. So this is the fundamental

of bitwise operators. Now in JavaScript we have a few more bitwise operators,

but in the real world they are not that common. Now let me give you

a real world example of when we can use these bitwise operators so

at least they make sense to you. Imagine we want to implement

an access control system. So the user can have

these permissions, read, write or

execute. Now we can use one

byte of information, or 8 bits, to determine the kind of information

a user can have. For example, we can use

5 0's 12345, we don't care about

the first 5 bits, but for the other 3 bits,

if the user has a permission we will use 1, otherwise we will

use 0. So if the user has only the read permission, you will use

1 for the read, and for write and execute you will

use 0. Similarly if the user has read and

write permissions. We can represent this permission

using this binary number. And finally if the user

has all these positions. We can represent that

like this. Now, this is where we use bitwise operators.

So, I'm going to delete these two lines, as well as

these few lines on the top, let's see how we can implement

these access control system, using bitwise operators. So,

I'm going to define a constant called readPermission,

now I need to set this to a decimal number that is

equivalent to this binary number. That decimal number is

4. Again, you can use an online converter to get this. Similarly

I'm going to define another constant, writePermission

now what I want now is the decimal representation

of this binary number. So all these bits

or flags are off, only the right flag is

on it, okay? So this binary number 10, is equivalent to

2 in the decimal system. And finally,

executePermission. So what we want is the

decimal representation of this binary number. All these flags

are 0, oney the execute flag or execute bit is

1. And that number is 1.

Now, I can declare a variable like myPermission

inititally set that to 0, now I can give myself extra

permissions. So, I can update my permission like

this, myPermission, here we apply the bit

wise or to add a permission like read

Permission, as well as the write

permission. Now let's take a look at the

value of my permission on the console.

So, we get 6. Now technically, we don't care about this decimal

number, we can use the bitwise and operator to see

if I have a given permission. So here's an example,

I'm going to declare a variable, let's call that message,

now here I'm going to use the ternary operator, the conditional

operator, remember? So we start with a. condition, we take

myPermission, and use the bitwise and operator along

with readPermission. Now,

if this evalues to true, that means I have the readPermission.

So, let's say you want to display a message like

yes, otherwise we want to display no.

Let me break this up into multiple lines so you can see clearly. So here's our

ternary operator. You have a condition, if that evalues to true, this

value will be used, otherwise this value will be used. Finally,

let's log this message on the console. So I

have the readPermission. But if I move this readPermission here,

and save the changes. Now, you can see

our readPermission is gone. So here's what I want you to take away.

With the bitwise or operator, we can add

permissions, and with the bitwise and operator, we can

check to see if we have a given permission. Of course this is just 1

real world use case for using the bitwise operators, there are other use cases

but as I told you before, they are really not that common, so if this

lecture was confusing, don't worry about it.