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

text stringlengths 1 81	start float64 0 10.1k	duration float64 0 24.9
[MUSIC PLAYING]	0	2.958
JORDAN HAYASHI: Hello, and welcome for Lecture Two--	17.27	2.37
React, Props, and State.	19.64	2.4
So last week, we talked about a bunch of different topics, one being ES6	22.04	3.72
and beyond and the syntax that comes with each of those.	25.76	2.69
We talked about closures, the process by which	28.45	2.62
a function can reference variables declared in a parent function.	31.07	5.13
We talked about IIFEs, Immediately Invoked Function Expressions.	36.2	3.68
We talked about using functions as first-class citizens.	39.88	3.675
We talked about the execution stack and event loop,	43.555	2.125
and how JavaScript actually executes in browsers.	45.68	2.82
We talked about callbacks, promises, and async/await, all of the different ways	48.5	3.3
to handle asynchronous actions.	51.8	1.89
And last, we talked about this and the way that this is bound.	53.69	3.96
This week, we're going to start with classes, which	57.65	3.23
is a syntax I was introduced in ES6.	60.88	3.639
It simplifies the defining of complex objects that have their own prototypes.	64.519	4.967
And with that, you have two different things.	69.486	1.874
You have classes and instances.	71.36	1.53
Classes is basically an abstract thing that you can declare,	72.89	3.73
basically saying, hey, by the way, any of these objects	76.62	2.78
that you create will have these methods associated with them.	79.4	3.03
Or they might have these things attached to them that you can use.	82.43	4.14
And then when you actually turn an abstract class	86.57	2.64
into an instance of that object, that is called an instance.	89.21	4.42
An example of that would be the difference between the date,	93.63	6.12
which is a function-- it's a class--	99.75	2.66
or a new date.	102.41	1.23
So if you do something like const d equals new date,	103.64	4.54
then now you have a date object itself.	108.18	3.38
And so Date with a capital D would be a class in that case,	111.56	3.137
and the lowercase D would be an instance.	114.697	1.708
These instances have things attached to them, like methods and properties,	120.61	3.54
and the classes have things like static methods.	124.15	2.4
And so methods are basically anything that's	126.55	2.07
a function that can be invoked on any of the instances.	128.62	4.12
You can think of that as a function on the classes prototype.	132.74	6.24
A static method, on the other hand, is basically	138.98	2.6
a method that doesn't really care about the particular instance of a class.	141.58	3.3
Instead, it cares about all instances of the class, so something like Date.now,	144.88	10.14
where you don't really care about a specific instance of a date	155.02	3.78
if you just want to get the time.	158.8	1.92
Whereas something like turning a date to a string--	160.72	2.62
in this class, d.toString--	163.34	3.625
in that case, you do care about the particular date	166.965	2.125
object that you're working on.	169.09	1.47
And so when you do capital Date.now, that's	170.56	2.91
considered a static method, since it's attached to the class.	173.47	2.97
And if you do something like date--	176.44	2.52
lowercase d-- dot toString, that really matters which instance you're attached	178.96	4.38
to, and therefore, that's a method.	183.34	2.71
Lastly, we have properties, which are like methods.	186.05	3.86
But rather than being functions, they're actually just values,	189.91	3.68
and they are associated with a particular instance of a class.	193.59	4.55
And so with classes come a few different keywords.	198.14	2.27
We have new, which you saw me type over here, which is basically saying,	200.41	3.91
hey, give me an instance of this particular class.	204.32	2.99
You invoke the class like an object, in case you want to pass anything into it.	207.31	3.32
And so say we want to do new const d2 equals new date,	210.63	5.362
and we actually want to pass in some number.	215.992	1.833
That gives us a new date from a very long time ago.	220.69	3.93
So d.toString.	224.62	1.29
Oh, d2.toString.	228.784	1.596
Since we passed in the number 1, 2, 3, 4, that's basically saying,	233.8	3.78
give me a date that's 1,234 milliseconds after date 0, which is back in 1969.	237.58	13.23
So a constructor is basically something that you	250.81	2
define within a class that says, hey, when you create a new class,	252.81	3.719
invoke this method such that you create a new instance of a class.	256.529	5.911
So let's actually practice this a little bit.	262.44	2.46
So is everybody here familiar with a data structure called a set?	264.9	3.075
So basically what a set is, is it's a list,	273.85	3.12
a data structure that supports things like add, delete, and inclusion,	276.97	4.5
where you cannot have multiple things of the same value.	281.47	3.62
Or in other words, it's a list of unique values.	285.09	2.84
And the methods that it should support are	287.93	2.51
add, which is basically add to this list;	290.44	2.46
delete, which is basically get rid of something from this;	292.9	3.06
or inclusion, which is saying, hey, does this list have a particular value?	295.96	5.97
And it should also have the ability to get its size.	301.93	2.54
And so down at the bottom of the file, I defined a few tests	304.47	4
that we're going to run after we implement this, such as line 7 here,	308.47	4.65
we have const s gets a new set with an array from 1 to 5,	313.12	4.17
which is basically saying, give me a new set with five values, 1, 2, 3, 4,	317.29	3.21
and 5.	320.5	1.09
We're going to try to do S.add1, and so we're	321.59	2.21
going to try to add 1 three times to the set.	323.8	3.37
And when we do S.size, we want it actually to only have five members,	327.17	4.31
because you shouldn't be able to add 1 multiple times.	331.48	4.17
Down here, we do S.add6, and then we try S.has6,	335.65	5.07
and it should contain the number 6.	340.72	2.67
That thing should not be there.	343.39	3.18
We try to see the size of it, and it should have added another member.	346.57	3.752
And then down here, we tried to delete that and do a couple	350.322	2.458
of associated checks with that.	352.78	1.85
And so how are we going to go about implementing this class?	354.63	3.22
So as per the slide over here, we use a method called constructor	361.22	3.8
in order to go ahead and construct an instance of this class.	365.02	4.18
And so within the class, we should have a method called constructor,	369.2	6.31
which takes a single argument.	375.51	3.55
It should take an array or some sort of list to be created with.	379.06	4.324

[MUSIC PLAYING]

0

2.958

JORDAN HAYASHI: Hello, and welcome for Lecture Two--

17.27

2.37

React, Props, and State.

19.64

2.4

So last week, we talked about a bunch of different topics, one being ES6

22.04

3.72

and beyond and the syntax that comes with each of those.

25.76

2.69

We talked about closures, the process by which

28.45

2.62

a function can reference variables declared in a parent function.

31.07

5.13

We talked about IIFEs, Immediately Invoked Function Expressions.

36.2

3.68

We talked about using functions as first-class citizens.

39.88

3.675

We talked about the execution stack and event loop,

43.555

2.125

and how JavaScript actually executes in browsers.

45.68

2.82

We talked about callbacks, promises, and async/await, all of the different ways

48.5

3.3

to handle asynchronous actions.

51.8

1.89

And last, we talked about this and the way that this is bound.

53.69

3.96

This week, we're going to start with classes, which

57.65

3.23

is a syntax I was introduced in ES6.

60.88

3.639

It simplifies the defining of complex objects that have their own prototypes.

64.519

4.967

And with that, you have two different things.

69.486

1.874

You have classes and instances.

71.36

1.53

Classes is basically an abstract thing that you can declare,

72.89

3.73

basically saying, hey, by the way, any of these objects

76.62

2.78

that you create will have these methods associated with them.

79.4

3.03

Or they might have these things attached to them that you can use.

82.43

4.14

And then when you actually turn an abstract class

86.57

2.64

into an instance of that object, that is called an instance.

89.21

4.42

An example of that would be the difference between the date,

93.63

6.12

which is a function-- it's a class--

99.75

2.66

or a new date.

102.41

1.23

So if you do something like const d equals new date,

103.64

4.54

then now you have a date object itself.

108.18

3.38

And so Date with a capital D would be a class in that case,

111.56

3.137

and the lowercase D would be an instance.

114.697

1.708

These instances have things attached to them, like methods and properties,

120.61

3.54

and the classes have things like static methods.

124.15

2.4

And so methods are basically anything that's

126.55

2.07

a function that can be invoked on any of the instances.

128.62

4.12

You can think of that as a function on the classes prototype.

132.74

6.24

A static method, on the other hand, is basically

138.98

2.6

a method that doesn't really care about the particular instance of a class.

141.58

3.3

Instead, it cares about all instances of the class, so something like Date.now,

144.88

10.14

where you don't really care about a specific instance of a date

155.02

3.78

if you just want to get the time.

158.8

1.92

Whereas something like turning a date to a string--

160.72

2.62

in this class, d.toString--

163.34

3.625

in that case, you do care about the particular date

166.965

2.125

object that you're working on.

169.09

1.47

And so when you do capital Date.now, that's

170.56

2.91

considered a static method, since it's attached to the class.

173.47

2.97

And if you do something like date--

176.44

2.52

lowercase d-- dot toString, that really matters which instance you're attached

178.96

4.38

to, and therefore, that's a method.

183.34

2.71

Lastly, we have properties, which are like methods.

186.05

3.86

But rather than being functions, they're actually just values,

189.91

3.68

and they are associated with a particular instance of a class.

193.59

4.55

And so with classes come a few different keywords.

198.14

2.27

We have new, which you saw me type over here, which is basically saying,

200.41

3.91

hey, give me an instance of this particular class.

204.32

2.99

You invoke the class like an object, in case you want to pass anything into it.

207.31

3.32

And so say we want to do new const d2 equals new date,

210.63

5.362

and we actually want to pass in some number.

215.992

1.833

That gives us a new date from a very long time ago.

220.69

3.93

So d.toString.

224.62

1.29

Oh, d2.toString.

228.784

1.596

Since we passed in the number 1, 2, 3, 4, that's basically saying,

233.8

3.78

give me a date that's 1,234 milliseconds after date 0, which is back in 1969.

237.58

13.23

So a constructor is basically something that you

250.81

2

define within a class that says, hey, when you create a new class,

252.81

3.719

invoke this method such that you create a new instance of a class.

256.529

5.911

So let's actually practice this a little bit.

262.44

2.46

So is everybody here familiar with a data structure called a set?

264.9

3.075

So basically what a set is, is it's a list,

273.85

3.12

a data structure that supports things like add, delete, and inclusion,

276.97

4.5

where you cannot have multiple things of the same value.

281.47

3.62

Or in other words, it's a list of unique values.

285.09

2.84

And the methods that it should support are

287.93

2.51

add, which is basically add to this list;

290.44

2.46

delete, which is basically get rid of something from this;

292.9

3.06

or inclusion, which is saying, hey, does this list have a particular value?

295.96

5.97

And it should also have the ability to get its size.

301.93

2.54

And so down at the bottom of the file, I defined a few tests

304.47

4

that we're going to run after we implement this, such as line 7 here,

308.47

4.65

we have const s gets a new set with an array from 1 to 5,

313.12

4.17

which is basically saying, give me a new set with five values, 1, 2, 3, 4,

317.29

3.21

and 5.

320.5

1.09

We're going to try to do S.add1, and so we're

321.59

2.21

going to try to add 1 three times to the set.

323.8

3.37

And when we do S.size, we want it actually to only have five members,

327.17

4.31

because you shouldn't be able to add 1 multiple times.

331.48

4.17

Down here, we do S.add6, and then we try S.has6,

335.65

5.07

and it should contain the number 6.

340.72

2.67

That thing should not be there.

343.39

3.18

We try to see the size of it, and it should have added another member.

346.57

3.752

And then down here, we tried to delete that and do a couple

350.322

2.458

of associated checks with that.

352.78

1.85

And so how are we going to go about implementing this class?

354.63

3.22

So as per the slide over here, we use a method called constructor

361.22

3.8

in order to go ahead and construct an instance of this class.

365.02

4.18

And so within the class, we should have a method called constructor,

369.2

6.31

which takes a single argument.

375.51

3.55

It should take an array or some sort of list to be created with.

379.06

4.324