Node Ecosystem, TDD, CI/CD

• Array.map()

  it’s a method creates a new array with the results of calling a function for every array element and it does not execute the function for empty elements and it does not change the original array.

• Array.reduce()

  this method executes a user-supplied “reducer” callback function on each element of the array, passing in the return value from the calculation on the preceding element. The final result of running the reducer across all elements of the array is a single value.

• promises

  A promise is an object that may produce a single value some time in the future either a resolved value, or a reason that it’s not resolved

callback functions

callback doesn’t make a function asynchronous. There are many examples of functions that take a function argument but are not asynchronous.