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TypeScript

TypeScript understands JavaScript and uses type inference to give you great tooling without additional code.

TypeScript is ideal thanks to its language features and type system, which enforce correctness and reduce the likelihood of bugs. By modeling the domain accurately, we aim to use the TypeScript transpiler to catch errors early and prevent them from propagating to runtime.

  • You can find the source code for the fmodel-ts here
  • Publicly available at npmjs.com

Decide​

(command: C, state: S) => readonly E[]

On a higher level of abstraction, any information system is responsible for handling the intent (Command) and based on the current State, produce new facts (Events):

  • given the current State/S on the input,
  • when Command/C is handled on the input,
  • expect list of new Events/E to be published/emitted on the output

Evolve​

(state: S, event: E) => S

The new state is always evolved out of the current state S and the current event E:

  • given the current State/S on the input,
  • when Event/E is handled on the input,
  • expect new State/S to be published on the output

Two functions are wrapped in a datatype class (algebraic data structure), which is generalized with three generic parameters:

export class Decider<C, S, E> implements IDecider<C, S, E> {
    constructor(
        readonly decide: (c: C, s: S) => readonly E[],
        readonly evolve: (s: S, e: E) => S,
        readonly initialState: S
    ) {
    }
}

Further reading​

Read more