Polymorphic function dispatch

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001.1.09 years ago9 years agoMinified + gzip package size for polymorf in KB


polymorf Build Status Dependency Status
Create a polymorphic function that dispatches to different handler functions based on the type of the parameters it is passed.


var add = polymorf(
  [Number, Number],
  function (a, b) {
    return a + b
  [String, String],
  function (a, b) {
    // Don't concat
    return parseFloat(a) + parseFloat(b)

add(2, 3) // 5
add('10', '12') // 22


polymorf([signature, handler] [, [signature, handler] ...])

Create a new polymorphic function. Arguments are signature, handler pairs, where signature is an array of types and handler is the function to be called if the polymorphic function is called with arguments whose types match the signature.

Allowed types

The following types are permitted as values in the signature array.
  • Object
  • Function
  • String
  • Error
  • Number
  • Array
  • Boolean
  • RegExp
  • Date
  • null
  • undefined

You can also pass your own custom types. Internally polymorf will check if values match the type in the signature using the instanceof operator.
Use the polymorf.Any type matcher to match any value.

fn.polymorf.add(signature, handler)

Given a polymorphic function fn, a new handler for a signature can be dynamically added. e.g.
var doubler = polymorf()

try {
    doubler(4) // Throws
} catch (er) {
    console.error('No signatures to match against')

doubler.polymorf.add([Number], function (x) {
    return x * 2

doubler(4) // 8


Given a polymorphic function fn, an existing handler for a signature can be dynamically removed.