jsla - Module of the Month: LevelUp

Name: jsla - Module of the Month: LevelUp
Uploaded: 2014-08-28T00:00:00.000Z
Description: Module of the month is a segment that highlights one of the many npm modules that make Node.js so great. This month's module was LevelUp

by Jacob Lowe on Aug 28, 2014

Module of the month was a small series at jsla in which people of the community would give talks about a specific module in the nodejs ecosystem. This months talk was about LevelUp.

Transcripts (auto-generate)

00:07
the module i'll be going over today is
00:09
level up so what level up is is a high
00:13
level wrapper around a database called
00:15
leveldb
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and
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leveldb is actually a database that was
00:20
created by google it's an embedded
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database it's just a key value store
00:24
it's actually what backs indexeddb
00:27
on the google chrome browser it also i
00:30
think is in mariadb as kind of like a
00:32
cache layer
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for their values and also is in this
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really cool project called
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dat
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which is all about sharing information
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between servers and multiple databases
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uses it behind the scenes really cool
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project i suggest checking it out
00:48
so level up to install it you do npm
00:52
install level up
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but it does have a dependency of level
00:55
down that doesn't include inside of its
00:57
package.json because you can actually
00:59
swap it out for different things so to
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install it you need to do
01:04
npm install level up level down and then
01:07
save those or you could just do npm
01:09
install level
01:10
um i already have installed because it
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level down is does have some c-scripts
01:15
so it takes a little bit to install
01:17
but i do have installed in this repo um
01:20
so what i'm going to do is start
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building a an application with it so the
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first thing you do
01:25
is that you include level up into
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your app
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and then
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we're going to create a database and
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this is real simple you just say
01:47
level up
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and there might be a little bit of lag
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in between my typing and what's going on
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is
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on the screen
01:57
uh
01:58
we just pointed towards a local
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directory now this will actually build a
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database if it's not there already but
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if it will hook up to the existing
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database if there is one i've actually
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created one and has a little bit of data
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in it uh not too much um so now since we
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have an empty database we'll essentially
02:13
have an empty database um
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we're gonna want to do some uh actions
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against it's like put information inside
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of it so i'm gonna create this little
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log file so that way we can see the
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information coming out
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and i'm going to use that crazy bind
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method
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to make a little logging function
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and then
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so we want to put information in so with
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level uh up it's really easy i do db
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put
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and then
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a key
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and then
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a value
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um
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so i'm going to say jsla is effing
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awesome
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and then that takes a callback function
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because after the write is done it it
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lets me know so i'm just going to pass
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in a log
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and then i'm going to run it
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um and as you can see well you will see
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it didn't spit out anything which is
03:10
good because it actually the only thing
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that it will pass back is an error if it
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happens
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so it looks like we're all good so we
03:16
want to see you know now the next thing
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you want to do with
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a database is to actually read that
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information out that you've stored with
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it so what i'm going to do
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is i'm going to
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push this down and then say db.get
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and then we want to get jsla and then
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i'm going to pass it that log function
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we only have to pass the one uh two
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parameters with this one um
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the the key and the callback
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so i'm gonna save
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and then we'll go back to the console
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so
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now
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you see it brings back nola's effing
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awesome it's all right i mean those
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pretty cool but knows where the value of
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the error would be
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uh and then that is the the value of
04:05
that that key that we stored
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um
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so let's say i've been to jsla and i
04:11
don't think it's it's super effing
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awesome
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so
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let's say we're going to do a delete
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on this key
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don't worry don't worry
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so we're going to save that and then
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we're going to run it
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and this doesn't have anything as well
04:28
that comes out because it's supposed to
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just bring back an error
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um
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so we're all good so we've actually
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written things uh read things and then
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we've deleted things from the database i
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do think jsla is effing awesome so we're
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gonna we're gonna we're gonna run that
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again um just to put that back in the
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database
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uh so another cool thing
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about this module is that uh it has
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streaming
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um so what i'm gonna do is i'm gonna
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create a second database so db2 is level
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up
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and then we're just going to put in a
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random database name
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so that way you see that i don't you
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know i didn't
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pre-fill this
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so i'm going to create a
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read stream
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which to do this all you do is db dot
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create
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read stream
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and i'm also going to create a right
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stream because a level db or
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level up has both of them
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so db2
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dot
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create
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right stream
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cool
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so now i have a restream and a right
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stream and what i want to do is i want
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to essentially copy my whole entire
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first database and then pump it into the
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second database
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and we can do this real easy by saying
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read stream dot pipe
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into our right stream
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so i'm gonna run this it's not gonna do
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anything in the console because we're
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not catching any errors
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but we're gonna assume that everything
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went okay i mean didn't throw any really
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bad errors
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so now we want to see uh that
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information
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to see if it actually uh put it into
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that second database so i'm just going
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to go up into this read stream and
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change it to the second database
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and then i'm going to take my read
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stream and say on
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data
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and then we're just going to
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use the log function as our callback
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now i'm gonna go back over and run it
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as you can see i had a couple little
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bits of information already in there
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in the first database but now this is
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the second database that we just created
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on the fly and pumped all the
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information from the first database into
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the second database using streaming
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so that's a level up i encourage you
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guys to to use it it's a very cool
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module
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and thank you
07:03
you