🐡 TIL 0208

⬇️ Main Note
https://docs.google.com/document/d/1Ce2r1obYEdFcmE1S8LLDWiZJbWWA0V6iE_wj4J9802k/edit

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🔍[Search]

Mostly backend computer takes a big role in searching. Once the frontend computer requsts for searching a word, the backend copmuter responses with the wanted word. then frontend receives it and displays to the screen.

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🔧 Types of Database

Full Table Scan

: This database scans the whole thing.

• ex) When the user is using searching method to look up for the posts that contain "Italy", full table scan database is scanning all the millions of posts.
• It's inefficient way to do so.
• Disk based database
  

Elastic Search

So to make sure the program runs in an efficient way, elastic search database can be used.

• Inside the database, the words are separated as tokens in the table.
  --> ex) "Hello Word" => Hello World
• Then the words of row are saved as a number so that the user can take out that specific number of row, which contains same words.
• Each words are seen as tokens, so this database action is called as tokenizing.
• This is way much faster.
• Disk based database

Redis

• High traffic === High connection volume
  --> More the traffic goes higher, more the searching keywords overlap.
• When things start to overlap much, new database is created: Reis.
• In this database, the searching keywords are saved in the table.
• "Cashing in redis" => Temporally save the keyword.
• Memory based database
  --> Fast
  

Disk based vs. Memory based

Memory based: Temporal saving.
--> Once the computer is shut down, all the data are gone.
--> Fast since it doesn't have to permanently save everything.
(일단 짱박아두는 개념)

Disk based: Permanent saving.
--> Doesn't get deleted even when the computer is shut down.
--> Slow since it has to save the data safely.
(디스크 자체에 저장)

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🕓 Debouncing vs. Throttle

Debouncing

• Operated when the user doesn't make any changes in input box for particular seconds.
• The user can assign the time.
  ex) 10 sec --> 10000
  Then 10 secs after making a change in input box, the request is sent.

Throttle

• Opposite concept of debouncing.
• Operated at the very first time when the browser is executed. After it is operated, for the assigned time, it doesn't send any request.
• ex) One scrolling literally looks like is is only scrolled once, but it is actually scrolled for millions of scrollings.
  --> To prevent million times of execution, throttle exists.

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👓 [Lodash]

• underbar is used as variables. _
• setTimeout: Function is executed after the particular time
  --> Debounce is used here.

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🥽 [Secret Code]

• #$%
  --> This might be much more complex since some users might accidentally type this.
  --> But for here, used #$% just for instance.
• So spliting the sentence in 3 values and save it inside the array.
• replaceAll -> split -> map
  

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👟 [Algorithms - Euclidean algorithm]

//유클리드 호재법 => 최대공약수를 구하기 위한 알고리즘 공식

//큰 수를 작은 수로 나눴을때 (a가 큰 수이고 b가 작은수라면 --> a를 b로 나눈다.)
//나머지 값이 6이 되면 나눴던 작은 수 b가 최대공약수가 된다
//나머지 값이 0이 될 때까지 계속 반복
//나머지가 0이 되면, 나눴던 작은 수 b가 최대공약수가 된다

function solution(n, m) {
  let a = m; //큰 수가 들어온다
  let b = n; //작은 수가 들어온다
  let r = 0; //a를 b로 나눴을 때의 나머지 값

  while (a % b > 0) {
    r = a % b;
    a = b; //큰 수에 작은 수를 할당
    b = r; //작은 수에는 나머지 값 할당
  }

  //최소공배수: n과 m을 곱한 값에 최대공약수를 나누면 최소공배수가 된다
  return [b, (n * m) / b];
}