Parse, Don't Validate

Based on Alexis King's article: https://lexi-lambda.github.io/blog/2019/11/05/parse-don-t-validate/

A parser is a function that consumes less-structured input and produces more-structured output. Validation checks a property and throws it away. Parsing checks a property and preserves it in the type system. Always prefer parsing.

The Core Idea

// VALIDATION: checks a property, returns nothing useful
function validateNonEmpty(list: string[]): void {
  if (list.length === 0) throw new Error("list cannot be empty");
}