pre-view/CS50-raw · Datasets at Hugging Face

text stringlengths 1 81	start float64 0 10.1k	duration float64 0 24.9
And what are we going to do?	383.384	1.166
Well, we should attach to the instance the array.	384.55	6.01
And that's basically saying, when I'm constructed,	390.56	2.38
I expect to have one argument, which is just an array.	392.94	3
And the only thing I'm going to do when creating this set object	395.94	3.87
is just store a reference to that array.	399.81	3.33
By doing this.arr = arr.	403.14	1.68
And so in this case, the this keyword is referring	407.33	2.71
to the instance of the object.	410.04	4.36
Cool, so let's try adding a couple of different methods to this.	414.4	3.44
So we should be able to support add, which should take a value.	417.84	5.88
We should be able to support delete, which also takes a value.	423.72	5.39
And we should have something called has, which checks for inclusion.	429.11	6.62
So how might we do something?	435.73	3.2
How might we add to this class?	438.93	1.594
Does anybody have any ideas?	440.524	1.166
AUDIENCE: [INAUDIBLE]	446.78	3.76
JORDAN HAYASHI: Exactly.	450.54	1
So we should use something like push to add to the array.	451.54	3.6
But before we do that, we should make sure that that number does not already	455.14	4.35
exist.	459.49	0.85
And so maybe we should implement the has method first, which is a great idea.	460.34	4.626
Let's go ahead and do that.	464.966	1.124
So how might we do has?	466.09	3.39
Well, it turns out on the array prototype,	469.48	2.19
we already have something called includes, which tells us	471.67	3.222
if an array includes a value, so we can just do that.	474.892	2.208
We can do return this.arr.includes(val).	477.1	2.98
And so now that we have that, how might we take care of add?	486.23	2.68
We should say, oh, well, if this does not have the value already, add to it.	492.43	8.3
And so here I use this.has.	506.08	3.15
So this here is referring to the instance of the set,	509.23	5.37
and so this.has is referring to this method	514.6	2.459
down here, on this particular instance.	517.059	3.411
And then when I do this.arr, this still refers to the instance of this set.	520.47	5.78
And so we're just getting at this array property that we have,	526.25	3.53
and we're pushing that value to that array.	529.78	3.25
Cool.	533.03	0.5
So how might we go about this delete?	533.53	2.475
AUDIENCE: [INAUDIBLE] has value.	540.718	2.119
JORDAN HAYASHI: Yeah, we can check if we have the value,	542.837	2.333
but it doesn't really matter all that much.	545.17	2.27
A quick and easy way would just be doing this.arr = this.arr.filter	547.44	6.691
and then we can just filter by the values.	554.131	1.749
So we could say, oh, we want for every x in here,	555.88	4.17
we want the x's that don't equal this value.	560.05	2.56
Cool.	568.14	0.5
And so we can go ahead and run this to see if it works.	568.64	2.39
Oops.	578.945	0.5
While I edit, I should flip these.	585.88	1.77
And we go ahead.	593.96	1.739
S should have five members and actually has-- ooh, we forgot to influence size,	595.699	3.291
actually.	598.99	0.5
And so we took care of all of the methods,	601.9	2.19
but we didn't include the size.	604.09	3.45
And so we should be able to return the size of this set.	607.54	3.84
How might we do that?	611.38	1.05
Well, this is interesting.	615.247	1.083
So we should be able to get at this value by doing the instance.size.	616.33	6.9
And JavaScript actually has a convenient way.	623.23	2.17
We can do get size, which is saying, when	625.4	8.26
somebody tries to get at the value or the property.size,	633.66	4.2
actually run this function.	637.86	2.41
So this is just syntax for that shortcut.	640.27	4.94
So how might we implement size?	645.21	1.81
AUDIENCE: [INAUDIBLE]	650.713	2.397
JORDAN HAYASHI: Yeah, just return this.arr.length.	653.11	3.09
So now we can run this, and we see I should have five members,	661.13	5.589
and it actually has five.	666.719	1.041
So that's good.	667.76	1.41
S should contain 5.	669.17	1.03
That's true.	670.2	0.5
That works.	670.7	1.06
S should contain six.	671.76	0.95
It's true.	672.71	0.93
S should have six members, and actually has six, so we're good still.	673.64	3.2
S should no longer contain six.	676.84	1.54
That also returns true.	678.38	1.53
And lastly, S should have five members, and actually does indeed have five.	679.91	5.34
So does anybody have any questions with our implementation of set as a class?	685.25	4.39
Great.	693.47	0.5
So it turns out JavaScript actually already has a set class,	693.97	7.1
and it works exactly as we implemented.	701.07	2.49
But say we actually wanted to use the native implementation of set	703.56	3.18
and actually add some stuff to it.	706.74	2.91
So that's where we use these other keywords, called extends and super.	709.65	3.7
So extends is the JavaScript way of saying,	713.35	2.31
hey, I want to start with a base class and actually add to it.	715.66	2.66
Extend this class.	718.32	1.83
And super, as we'll see in a second, is when we're writing that class,	720.15	3.016
so we can refer to the original class using this keyword.	723.166	2.374
And so in this example called my set, we're	730.49	2.27
going ahead and extending that set with a bunch of different things.	732.76	3.197
And so here you see constructor.	735.957	1.333
It still takes an array.	737.29	1.08
And the first thing that we do is we invoke super on that array.	738.37	3.87
So this is basically saying, hey, we're extending a set.	742.24	5.769
So when you do the constructor, the first thing you should do	748.009	2.541
is actually run the original set's constructor.	750.55	3.69
And then let's also keep track of this.originalarray	754.24	2.23

And what are we going to do?

383.384

1.166

Well, we should attach to the instance the array.

384.55

6.01

And that's basically saying, when I'm constructed,

390.56

2.38

I expect to have one argument, which is just an array.

392.94

3

And the only thing I'm going to do when creating this set object

395.94

3.87

is just store a reference to that array.

399.81

3.33

By doing this.arr = arr.

403.14

1.68

And so in this case, the this keyword is referring

407.33

2.71

to the instance of the object.

410.04

4.36

Cool, so let's try adding a couple of different methods to this.

414.4

3.44

So we should be able to support add, which should take a value.

417.84

5.88

We should be able to support delete, which also takes a value.

423.72

5.39

And we should have something called has, which checks for inclusion.

429.11

6.62

So how might we do something?

435.73

3.2

How might we add to this class?

438.93

1.594

Does anybody have any ideas?

440.524

1.166

AUDIENCE: [INAUDIBLE]

446.78

3.76

JORDAN HAYASHI: Exactly.

450.54

1

So we should use something like push to add to the array.

451.54

3.6

But before we do that, we should make sure that that number does not already

455.14

4.35

exist.

459.49

0.85

And so maybe we should implement the has method first, which is a great idea.

460.34

4.626

Let's go ahead and do that.

464.966

1.124

So how might we do has?

466.09

3.39

Well, it turns out on the array prototype,

469.48

2.19

we already have something called includes, which tells us

471.67

3.222

if an array includes a value, so we can just do that.

474.892

2.208

We can do return this.arr.includes(val).

477.1

2.98

And so now that we have that, how might we take care of add?

486.23

2.68

We should say, oh, well, if this does not have the value already, add to it.

492.43

8.3

And so here I use this.has.

506.08

3.15

So this here is referring to the instance of the set,

509.23

5.37

and so this.has is referring to this method

514.6

2.459

down here, on this particular instance.

517.059

3.411

And then when I do this.arr, this still refers to the instance of this set.

520.47

5.78

And so we're just getting at this array property that we have,

526.25

3.53

and we're pushing that value to that array.

529.78

3.25

Cool.

533.03

0.5

So how might we go about this delete?

533.53

2.475

AUDIENCE: [INAUDIBLE] has value.

540.718

2.119

JORDAN HAYASHI: Yeah, we can check if we have the value,

542.837

2.333

but it doesn't really matter all that much.

545.17

2.27

A quick and easy way would just be doing this.arr = this.arr.filter

547.44

6.691

and then we can just filter by the values.

554.131

1.749

So we could say, oh, we want for every x in here,

555.88

4.17

we want the x's that don't equal this value.

560.05

2.56

Cool.

568.14

0.5

And so we can go ahead and run this to see if it works.

568.64

2.39

Oops.

578.945

0.5

While I edit, I should flip these.

585.88

1.77

And we go ahead.

593.96

1.739

S should have five members and actually has-- ooh, we forgot to influence size,

595.699

3.291

actually.

598.99

0.5

And so we took care of all of the methods,

601.9

2.19

but we didn't include the size.

604.09

3.45

And so we should be able to return the size of this set.

607.54

3.84

How might we do that?

611.38

1.05

Well, this is interesting.

615.247

1.083

So we should be able to get at this value by doing the instance.size.

616.33

6.9

And JavaScript actually has a convenient way.

623.23

2.17

We can do get size, which is saying, when

625.4

8.26

somebody tries to get at the value or the property.size,

633.66

4.2

actually run this function.

637.86

2.41

So this is just syntax for that shortcut.

640.27

4.94

So how might we implement size?

645.21

1.81

AUDIENCE: [INAUDIBLE]

650.713

2.397

JORDAN HAYASHI: Yeah, just return this.arr.length.

653.11

3.09

So now we can run this, and we see I should have five members,

661.13

5.589

and it actually has five.

666.719

1.041

So that's good.

667.76

1.41

S should contain 5.

669.17

1.03

That's true.

670.2

0.5

That works.

670.7

1.06

S should contain six.

671.76

0.95

It's true.

672.71

0.93

S should have six members, and actually has six, so we're good still.

673.64

3.2

S should no longer contain six.

676.84

1.54

That also returns true.

678.38

1.53

And lastly, S should have five members, and actually does indeed have five.

679.91

5.34

So does anybody have any questions with our implementation of set as a class?

685.25

4.39

Great.

693.47

0.5

So it turns out JavaScript actually already has a set class,

693.97

7.1

and it works exactly as we implemented.

701.07

2.49

But say we actually wanted to use the native implementation of set

703.56

3.18

and actually add some stuff to it.

706.74

2.91

So that's where we use these other keywords, called extends and super.

709.65

3.7

So extends is the JavaScript way of saying,

713.35

2.31

hey, I want to start with a base class and actually add to it.

715.66

2.66

Extend this class.

718.32

1.83

And super, as we'll see in a second, is when we're writing that class,

720.15

3.016

so we can refer to the original class using this keyword.

723.166

2.374

And so in this example called my set, we're

730.49

2.27

going ahead and extending that set with a bunch of different things.

732.76

3.197

And so here you see constructor.

735.957

1.333

It still takes an array.

737.29

1.08

And the first thing that we do is we invoke super on that array.

738.37

3.87

So this is basically saying, hey, we're extending a set.

742.24

5.769

So when you do the constructor, the first thing you should do

748.009

2.541

is actually run the original set's constructor.

750.55

3.69

And then let's also keep track of this.originalarray

754.24

2.23