cascade

Small set of utility functions that help implement conditional selection/execution of options/functions. Summary:

• Provide a set of ordered alternatives
• Each alternative consists of a criteria and a value
• For each alternative, test the criteria against a given input and find the corresponding value

It's like a switch statement that the cases are provided through an array of alternatives.

Executing corresponding function

import { [test](#testcriteria-args), [cascadeExec](#cascadeexectest-alternatives-args) } from '@orioro/cascade'

const alternatives = [
  [
    item => item.type === 'book',
    item => `${item.title} - por ${item.authors.join(' e ')}`
  ],
  [
    item => item.type === 'plant',
    item => `${item.name} (${item.scientificName})`
  ],
  [
    item => item.type === 'person',
    item => `${item.firstName} ${item.middleName} ${item.lastName}, ${item.profession}`
  ],
  [
    item => `Unknown: ${(item.name || item.title)}`
  ]
]

const summarize = item => cascadeExec(testFn, alternatives, item)

console.log(summarize({
  type: 'book',
  title: 'Psicogênese da Língua Escrita',
  authors: ['Emília Ferreiro', 'Ana Teberosky']
}))
// 'Psicogênese da Língua Escrita - por Emília Ferreiro e Ana Teberosky'

console.log(summarize({
  type: 'plant',
  name: 'Samambaiaçu',
  scientificName: 'Dicksonia sellowiana'
}))
// 'Samambaiaçu (Dicksonia sellowiana)'

console.log(summarize({
  type: 'person',
  firstName: 'João',
  lastName: 'Nunes',
  middleName: 'Silveira',
  profession: 'Desenvolvedor de software'
}))
// 'João Silveira Nunes, Desenvolvedor de software'

console.log(summarize({
  type: 'something_else',
  title: 'Something else'
}))
// 'Unknown: Something else'

Purpose

This pattern is geared towards allowing developers to expose APIs that allow users to compose and customize an algorithm's behavior. Lib developers can provide some built-in alternatives that resolve common situations and allow users to provide additional alternatives to solve domain-specific requirements.

Example usage at:

• https://github.com/orioro/node-tree-source-nodes
• https://github.com/orioro/node-nested-map

API

• Criteria
• Alternative
• Alternative
• TestFunction
• test(criteria, args)
• cascadeFind(test, alternatives, args)
• cascadeExec(test, alternatives, args)
• cascadeFind(test, alternatives, args)

Criteria

Function that returns boolean

Alternative

Tuple consisting of either:

• [Criteria, value]
• [value]

Alternative

Tuple consisting of either:

• [Criteria, Function]
• [Function]

TestFunction

Function that interprets a given criteria. Takes as arguments:

• {Criteria} criteria
• ...args Remaining arguments

test(criteria, args)

• criteria {Criteria}
• args {...args[]}

cascadeFind(test, alternatives, args)

• test {TestFunction}
• alternatives {[Alternative](#alternative)[]}
• args {...args[]}
• Returns: {*}

cascadeExec(test, alternatives, args)

• test {TestFunction}
• alternatives {Executable[Alternative](#alternative)[]}
• args {...args[]}
• Returns: {*}

cascadeFind(test, alternatives, args)

• test {TestFunction}
• alternatives {[Alternative](#alternative)[]}
• args {...args[]}
• Returns: {*[]}