zwitch

Handle values based on a property.

Install

This package is ESM only: Node 12+ is needed to use it and it must be imported instead of required.

npm:

npm install zwitch

Use

import {zwitch} from 'zwitch'

var handle = zwitch('type', {invalid, unknown, handlers: {alpha: handleAlpha}})

handle({type: 'alpha'})

function handleAlpha() { /* … */ }

Or, with a switch statement:

var field = 'type'

function handle(value) {
  var fn

  if (!value || typeof value !== 'object' || !(field in value)) {
    fn = invalid
  } else {
    switch (value[field]) {
      case 'alpha':
        fn = handleAlpha
        break
      default:
        fn = unknown
        break
    }
  }

  return fn.apply(this, arguments)
}

handle({type: 'alpha'})

function handleAlpha() { /* … */ }

API

This package exports the following identifiers: zwitch. There is no default export.

zwitch(key[, options])

Create a functional switch, based on a key (string).

options

Options can be omitted and added later to one.

• handlers (Object.<Function>, optional) — Object mapping values to handle, stored on one.handlers
• invalid (Function, optional) — Handle values without key, stored on one.invalid
• unknown (Function, optional) — Handle values with an unhandled key, stored on one.unknown

Returns

Function — See one.

one(value[, rest…])

Handle one value. Based on the bound key, a respective handler will be called. If value is not an object, or doesn’t have a key property, the special “invalid” handler will be called. If value has an unknown key, the special “unknown” handler will be called.

All arguments, and the context object, are passed through to the handler, and it’s result is returned.

one.handlers

Map of handlers (Object.<string, Function>).

one.invalid

Special handler called if a value doesn’t have a key property. If not set, undefined is returned for invalid values.

one.unknown

Special handler called if a value does not have a matching handler. If not set, undefined is returned for unknown values.

function handler(value[, rest…])

Handle one value.

Related

• mapz — Functional map

License

MIT © Titus Wormer