Hooks

Hooks can be used to enable custom behavior. They are called at specific points either before (pre) or after (post) a specific action is performed. This offers the ability to eventually manipulate data before being processed or to perform additional actions after a specific action has been performed.

The useHooks function acts as a wrapper and allows to register optional pre- or post-hook functions. It returns a function that can be called as usual, but will eventually call the registered hooks before and after the actual function is called.

// useHooks(fn, name, hooks)(arguments));
const hooks = {
  preLog: (params, ...args) => {
    console.log('preLog', { params, args });
    params.fn(...args); // call the actual function
    return 'lol';
  },
  postLog: (params, ...args) => {
    console.log('postLog', { params, args });
  },
};

const log = useHooks(console.log, 'Log', hooks); // Wrap the function
log('foo', 'bar');

// Outputs:
// preLog { params: { fn: [Function: log] }, args: [ 'foo', 'bar' ] }
// foo bar
// postLog { params: { fn: [Function: log], result: 'lol' }, args: [ 'foo', 'bar' ] }

note

pre and post are prepended to the case-sensitive hooks name (preLog, not prelog).

The pre- and post-hook functions get called with the params object, containing the actual function fn and the optional result.

type HookFn<T extends (...args: any[]) => any> = (
  params: Parameter<Parameters<T>, ReturnType<T>>,
  ...args: Parameters<T>
) => ReturnType<T>;

preHookFn

The preHookFn gets called before the actual function is called. The first parameter is the params object, containing the actual function fn.

params.fn has to be called manually to execute the actual function.

function preHookFn(params, ...args) {
  // do something before the actual function is called
  return params.fn(...args); // call the actual function
}

postHookFn

The postHookFn gets called after the actual function is called. The first parameter is the params object, containing the actual function fn and the result from the eventually calles fn.

function postHookFn(params, ...args) {
  // do something after the actual function is called
  return params.result; // return the result from the previous call
}