Four Ways to Compose Synchronous Functions in JavaScript: Nest, Promise, Compose, & Pipeline


Functional Programming is built around composing pure functions. Composing functions means taking all those useful functions you wrote and using them together to build more powerful functions, and even applications. This article will cover the 4 main ways to do that with synchronous code which includes the new pipeline operator. A future article will handle asynchronous options as well as dealing with partial applications and curried functions. If you’d like to play with the examples yourself, I have a Code Sandbox setup with basic and advanced examples.

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What Are Partial Applications?


A Partial Application is a function where some or all of the arguments are packed inside, ready to go and it’s just waiting for a few more before the main function is invoked. They’re like functions that have default arguments, but are pure functions with a fixed amount of parameters.


The following article and companion video playlist will cover what a partial application is and how it can be used for a more pure function option for default arguments. It’s assumed you know what pure functions are. We’ll cover:

  • basic function arguments
  • default arguments and how order can make them harder/easier to use
  • function arity
  • function currying with closures and show how the parameter order is reversed compared to default arguments
  • building partial applications to show how to make using default arguments pure
  • creating partial applications with no arguments
Continue reading “What Are Partial Applications?”