The comparison between TypeScript (TS) and PureScript (PS) highlights key differences in their handling of immutability and mutability when compiling to JavaScript. While both languages enforce restrictions to increase code reliability, PureScript is immutable by default, making it inherently suitable for pure functions, whereas TypeScript, being mutable by default, requires specific syntax to manage immutability, such as Readonly and const assertions. This distinction affects how each language manages state and operations like the quicksort algorithm, where PureScript's immutable approach contrasts with TypeScript's mutable one, highlighting the ergonomic shifts based on language defaults. Moreover, PureScript's use of types like ST and STRef for handling local mutations ensures safety and encapsulation, preventing unintended side effects, thus promoting a more controlled environment for mutable operations. The article suggests that the choice between mutation and immutability may depend on practical considerations, with a preference towards immutability unless convenience outweighs associated risks.