/typescript_pgpromise

Primary LanguageTypeScript

Typescript Interview Test

  1. Install postgres & nodejs
  2. Create the test database using the ./createdb.sh script
  3. Install the npm_modules for this project running npm install
  4. Run npm run test to get the program running (modify the user and password if needed)
  5. Examine the typescript code under server.ts

Using the library ramda, what is the result of the following code?

R.reduce((acc,x) => R.compose(R.flip(R.prepend)(acc), R.sum,R.map(R.add(1)))([x,...acc]), [0])([13, 28]);

I didn't understand the full code snippet. But, I got some points:

The anonymous function, call itself passing an array with two numbers.

Reduce is called passing the list of numbers and current iterator.

Compose function reverses functions composition, like right-to-left, the first becomes the last.

Add function is simple as a + b; But used with R.map apply the function to every element of the list.

The function R.sum, Adds all the elements of a list supplied.

The functions R.prepend, R.flip the mode of use, just made my head blow, i didn't get the point.

If the tables become too big / the accesses too slow, what would you do to improve its speed?

Never use SELECT * FROM .... Ask only required fields.

Create some indexes becouse without indexes, every request to the DB would lead to a full scan of the entirety of the table to find results.

We could use cache to answer for some common queries .

PostgreSQL read-only replicas provide a great way to reduce the load on the main DB. It could be a great way to improve its speed.