What is functional programming?

Information drawn from

• Why functional programming
• Functional Programming Fundamentals

Functional programming is a programming paradigm that expresses a computation directly as pure functional transformation of data.

 A functional program can be viewed as a declarative program where computations are specified as pure functions.

Pure functions is a function that returns always the same value for the same input and has no side effects.

In constrast to imperative programming (which describe how to does something) , functional programming describe what to to instead of how to do it.

Javascript example using Imperative approach

function getFileMapById(files) {
  const fileMap = {};
  for (let i = 0; i < files.length; i++) {
    const file = files[i];
    fileMap[file.id] = file;
  }
  return fileMap
}

Same example using Declarative/Functional approach

function getFileMapById(files) {
  return lodash.keyBy(files, "id")
}

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Last update on 09 Jan 2020

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