Store-passing style is a programming technique that is used to model mutable state without using mutable state.
[1][2] It generally arises in the conversion of imperative programs into purely functional ones.
So, for instance, consider this JavaScript program, written in a non-store-passing-style: This contains a reference to a global variable.
The code might look like this: Note that each call takes an extra argument, and two values are now returned; the ordinary return value, and a new value representing the state of the formerly mutable variable.
Store-passing style can be quite painful to write, but can help to eliminate race conditions by isolating state within function calls, and can potentially make code more parallelizable.