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let's change this back to 0. | 4,985.63 | 1.17 |
And so now as you notice it is
showing that 0 value as expected. | 4,990.8 | 3.485 |
But let's actually call
this something else. | 4,997.29 | 2.68 |
So let's call this custom Count. | 4,999.97 | 2.98 |
So even though over here we're
exporting a variable called | 5,009.98 | 4.92 |
Count, since we're are using
it as a default export, | 5,014.9 | 4.89 |
we can import the default export in
this file and call it whatever you want. | 5,019.79 | 5.54 |
And so we can call it custom Count over
here and it still works as expected. | 5,025.33 | 5.06 |
And so the difference between named
and default exports are that named, 1, | 5,030.39 | 4.67 |
you can export multiple
of named exports and also | 5,035.06 | 5.4 |
import to multiple named
exports from a different file. | 5,040.46 | 3.96 |
And they do have to be named exactly
as they are in the other files. | 5,044.42 | 5.68 |
But when you export
something default you're | 5,050.1 | 2.15 |
limited to only exporting
one which makes sense. | 5,052.25 | 2.52 |
If you exported multiple defaults you
wouldn't know which one to import. | 5,054.77 | 4.317 |
And then over here, you
can call it whatever | 5,059.087 | 1.833 |
you want because it doesn't matter,
it's just the default export. | 5,060.92 | 5.16 |
And so that's how you're
going to go about starting | 5,066.08 | 2.37 |
to remove components from one long
file and move them into separate files. | 5,068.45 | 7.09 |
And so you can also actually import the
export default and also named exports. | 5,075.54 | 10.37 |
So here we are exporting a named export
and we're also having a default export. | 5,090.33 | 7.11 |
And in here we're importing the default
and we're also importing a named export | 5,097.44 | 7.9 |
and, as you see, that works as well. | 5,105.34 | 2.44 |
And so over here you see that we
are importing React from React which | 5,110.72 | 5.2 |
is whatever its default export is. | 5,115.92 | 3.57 |
We could also import one
of its named exports, | 5,119.49 | 5.67 |
and rather than extending
a React.component | 5,125.16 | 2.84 |
we can just extend
component here because we | 5,128 | 4.3 |
went ahead and imported the named
export called component from React. | 5,132.3 | 4.74 |
And so that will also work as well. | 5,137.04 | 2.14 |
So any questions on
importing and exporting | 5,143.89 | 2.72 |
and how you would go about
breaking up particular components | 5,146.61 | 3.66 |
into separate files? | 5,150.27 | 3.04 |
Yeah. | 5,153.31 | 1 |
AUDIENCE: You were able to access
the components with React.components. | 5,154.31 | 6.5 |
Is that because the component is
[INAUDIBLE] named export and the value | 5,160.81 | 6.5 |
in the React.components? | 5,167.31 | 2 |
SPEAKER 1: Yes exactly. | 5,169.31 | 1 |
So the question was, I was
able to access component | 5,170.31 | 3.83 |
as React.component and
separately also as component | 5,174.14 | 7.86 |
and that's because this thing
called component is actually | 5,182 | 3.69 |
a property on this React. | 5,185.69 | 4.56 |
And so what React exports is
both a default export, which | 5,190.25 | 4.11 |
is this massive thing where one of
its object keys is called a component | 5,194.36 | 7.29 |
and has the value of the component
and it's also separately exporting | 5,201.65 | 4.08 |
a named export called component. | 5,205.73 | 1.86 |
And so we can go ahead and either
import the default export and do that | 5,207.59 | 4.27 |
.component or we can import the
named component and just use that. | 5,211.86 | 3.61 |
So you're absolutely correct. | 5,215.47 | 1.92 |
Any other questions on
importing and exporting? | 5,221.23 | 2.99 |
Cool. | 5,227.93 | 0.5 |
So when we go ahead and
import and export components | 5,228.43 | 4.42 |
they can start to get more and more
complex as we pass down more props. | 5,232.85 | 5.26 |
And so how might we go about
keeping track of all of these props? | 5,238.11 | 4.22 |
Well React actually has a
way to help you with that, | 5,242.33 | 3.09 |
and it's called prop types. | 5,245.42 | 2.22 |
And so React can actually validate
the types of a given components props | 5,247.64 | 3.9 |
at runtime which is great. | 5,251.54 | 2.59 |
It's a development tool that
allows you as a developer | 5,254.13 | 3.09 |
to ensure that you're
passing the props that you | 5,257.22 | 2 |
think you're actually passing down. | 5,259.22 | 1.458 |
And so say you're passing
down some prop that's a number | 5,260.678 | 3.972 |
but you actually want it as a string. | 5,264.65 | 2.1 |
It's very easy, as your project scales
up, to kind of get those mixed up | 5,266.75 | 5.512 |
and maybe you pass down
a string when you meant | 5,272.262 | 1.958 |
to pass down a number or vise versa. | 5,274.22 | 3.31 |
And so this thing called PropTypes
allows you to keep track of that. | 5,277.53 | 4.31 |
And React will actually do this
automatically in development mode. | 5,281.84 | 4.75 |
And this is also great because
it helps document your APIs. | 5,286.59 | 2.78 |
And so I have this very simple
component over here called Count | 5,289.37 | 8.19 |
and it takes a single prop called Count. | 5,297.56 | 2.16 |
But say it also took
three other props and say | 5,299.72 | 2.825 |
it also had 10 other components
that also took their own props. | 5,302.545 | 5.365 |
It might get kind of hard to
remember that as I scale the project. | 5,307.91 | 4.11 |
And say you're somebody
like Facebook who | 5,312.02 | 1.8 |
have something like 30,000
different components in production | 5,313.82 | 3.69 |
it would be very painful to
not have those documented | 5,317.51 | 2.21 |
and have to go and read the code to
know exactly what props you should | 5,319.72 | 2.98 |
be passing. | 5,322.7 | 1.45 |
And so by declaring this
thing called PropTypes | 5,324.15 | 3.95 |
you actually can help self
document all of these APIs. | 5,328.1 | 3.59 |
And what's nice is this only
runs in development mode | 5,331.69 | 2.23 |
and so you don't have to
worry about it slowing down | 5,333.92 | 2.166 |
your production in production mode. | 5,336.086 | 3.604 |
And so how might we go about doing that? | 5,339.69 | 2.45 |
There's actually a
package called PropTypes. | 5,342.14 | 2.07 |
It used to be bundled as
part of React but they've | 5,344.21 | 2.91 |
since split it into its own
module though it's still | 5,347.12 | 5.73 |
maintained by Facebook. | 5,352.85 | 1.62 |
So we can go ahead and do this
thing called import PropTypes | 5,354.47 | 4.47 |
from a package called prop-types. | 5,358.94 | 1.95 |
And so now we have access to
this variable called PropTypes | 5,364.97 | 2.61 |
where importing the default export
of whatever this library called | 5,367.58 | 6.36 |
PropTypes is. | 5,373.94 | 1.63 |
And so now we can go ahead
and use that in our file. | 5,375.57 | 2.21 |
And so let's go ahead and do Count. | 5,377.78 | 4.2 |
And so we created this
variable called Count, | 5,381.98 | 3.25 |
which is a function of a
stateless functional component. | 5,385.23 | 3.78 |
And we can actually attached to
it a property called propTypes. | 5,389.01 | 6.48 |
Note that it's a lower case p here. | 5,395.49 | 2.3 |
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