Functional Programming Fundamentals

You refactor an impure function into a pure function by isolating side effects and ensuring referential transparency, making outputs depend entirely on inputs without modifying external state.

The best way to build complex logic from simple functions in JavaScript is using function composition and currying, which creates reusable building blocks through declarative data transformation pipelines.

Pointfree style reduces code noise in TypeScript functional programming by focusing on data transformations through function composition rather than explicit variable management, yielding highly maintainable and testable code architectures.

You should transition from imperative to declarative coding styles to solve the unpredictability of imperative code, achieving robust, predictable, and highly composable software systems that are significantly easier to debug and test.

You need currying and partial application in TypeScript when building advanced function pipelines, allowing you to pre-fill arguments and create highly composable, reusable building blocks for complex application development.