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
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  level up so what level up is is a high
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  level wrapper around a database called
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  leveldb
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  and
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  leveldb is actually a database that was
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  created by google it's an embedded
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  database it's just a key value store
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  it's actually what backs indexeddb
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  on the google chrome browser it also i
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  think is in mariadb as kind of like a
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  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
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  so level up to install it you do npm
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  install level up
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  but it does have a dependency of level
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  down that doesn't include inside of its
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  package.json because you can actually
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  swap it out for different things so to
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  install it you need to do
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  npm install level up level down and then
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  save those or you could just do npm
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  install level
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  um i already have installed because it
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  level down is does have some c-scripts
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  so it takes a little bit to install
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  but i do have installed in this repo um
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  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
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  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
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  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
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  uh
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  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
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  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
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  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
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  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
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  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
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  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
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  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
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  you