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createChain()

createChain<In, Out>(...handlers): (input) => Out

Creates a chain from an ordered list of handlers. Each handler can inspect the input and either:

  • return a result (short-circuit)
  • call next(input) to pass to the next handler

The last handler's next throws if called, since there is nothing after it. The last handler should always produce a result.

Type Parameters​

In: In​

The request/input type

Out: Out​

The response/output type

Parameters​

handlers: ...Handler<In, Out>[]​

Ordered list of handlers (first = outermost)

Returns​

A function that runs the chain

Since​

2.4.0

Example​

const log: `Handler<number, string>` = (n, next) => {
  console.log(`processing ${n}`);
  return next(n);
};

const double: `Handler<number, string>` = (n) => String(n * 2);

const chain = createChain(log, double);
chain(21); // logs "processing 21", returns "42"

Handler()<In, Out>​

Type

Handler<In, Out> = (input, next) => Out

A Handler receives an input and a next function. It can either return a result directly (stopping the chain) or call next(input) to delegate to the next handler.

The last handler in the chain receives a next that is never called - it must produce a result on its own.

Type Parameters​

In: In​

The request/input type

Out: Out​

The response/output type

Parameters​

input: In​

next: (input) => Out​

Returns: Out​

Since​

2.4.0