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zwitch
Advanced tools
Weekly downloads
Package description
The zwitch npm package is a utility for handling polymorphic dispatch based on a property value. It allows you to define a default handler and specific handlers for different values of a given property. This can be particularly useful for tasks like routing, handling different types of data structures, or implementing pattern matching in your code.
Handling different types of messages
This feature demonstrates how zwitch can be used to handle different types of messages based on their 'type' property. It shows setting up handlers for specific types and handling invalid or unknown types.
{"const zwitch = require('zwitch');\nconst handle = zwitch('type');\n\nhandle.invalid = (value) => { console.error('Invalid type:', value); };\nhandle.unknown = (value) => { console.error('Unknown type:', value); };\nhandle.handlers.string = (value) => { console.log('String:', value); };\nhandle.handlers.number = (value) => { console.log('Number:', value); };\n\nhandle({type: 'string', value: 'Hello, world!'});\nhandle({type: 'number', value: 42});\nhandle({type: 'boolean', value: true});"}
Default and specific handling
This feature illustrates using zwitch to define a default handler and a specific handler for the 'foo' key. It demonstrates how unhandled keys are processed by the default handler.
{"const zwitch = require('zwitch');\nconst handle = zwitch('key');\n\nhandle.default = (value) => { console.log('Default handler:', value); };\nhandle.handlers.foo = (value) => { console.log('Handled foo:', value); };\n\nhandle({key: 'foo', value: 'bar'});\nhandle({key: 'baz', value: 'qux'});"}
Similar to zwitch, this package allows for polymorphic function definitions based on the types of arguments. It differs in that it focuses on argument types rather than object properties.
This package provides functionality for pattern matching in JavaScript, similar to functional programming languages. It's comparable to zwitch in enabling conditional logic based on values, but it uses a different syntax and approach, focusing on matching patterns rather than dispatching based on property values.
Readme
Handle values based on a field.
This is a tiny package that lets you switch
between some field on objects.
This package is very useful when mapping one AST to another.
It’s a lot like a switch
statement on one field, but it’s extensible.
This package is ESM only. In Node.js (version 14.14+, 16.0+), install with npm:
npm install zwitch
In Deno with esm.sh
:
import {zwitch} from 'https://esm.sh/zwitch@2'
In browsers with esm.sh
:
<script type="module">
import {zwitch} from 'https://esm.sh/zwitch@2?bundle'
</script>
import {zwitch} from 'zwitch'
const handle = zwitch('type', {invalid, unknown, handlers: {alpha: handleAlpha}})
handle({type: 'alpha'})
function handleAlpha() { /* … */ }
Or, with a switch
statement:
const field = 'type'
function handle(value) {
let fn = invalid
if (value && typeof value === 'object' && field in value) {
switch (value[field]) {
case 'alpha':
fn = handleAlpha
break
default:
fn = unknown
break
}
}
return fn.apply(this, arguments)
}
handle({type: 'alpha'})
function handleAlpha() { /* … */ }
function unknown() { /* … */ }
function invalid() { /* … */ }
This package exports the identifier zwitch
.
There is no default export.
zwitch(key[, options])
Create a switch, based on a key
(string
).
options
Options can be omitted and added later to one
.
options.handlers
Handlers to use, stored on one.handlers
(Record<string, Function>
,
optional).
options.unknown
Handler to use for unknown values, stored on one.unknown
(Function
,
optional).
options.invalid
Handler to use for invalid values, stored on one.invalid
(Function
,
optional).
See one
(Function
).
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 (this
), are passed through to the
handler, and it’s result is returned.
one.handlers
Map of handlers (Record<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.
This package is fully typed with TypeScript.
It exports the types Handler
, UnknownHandler
, InvalidHandler
, and
Options
.
This package is at least compatible with all maintained versions of Node.js. As of now, that is Node.js 14.14+ and 16.0+. It also works in Deno and modern browsers.
mapz
— functional mapYes please! See How to Contribute to Open Source.
This package is safe.
FAQs
Handle values based on a property
The npm package zwitch receives a total of 5,676,967 weekly downloads. As such, zwitch popularity was classified as popular.
We found that zwitch demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 1 open source maintainer collaborating on the project.
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