decision-table

When you dont want a lot of ugly if statments. Provides a compact decision logic in a table-like layout.

install

npm i decision-table 

usage

var DecisionTable = require('decision-table')

var table = new DecisionTable(
  ['type', 'count', 'applied', 'emotion'],
  [
    ['a', 1, true,  'happy', 1],
    ['a', 1, true,  'sad',   2],
    ['a', 1, false, 'happy', 3],
    ['a', 1, false, 'sad',   4],
    ['a', 2, true,  'happy', 5],
    ['a', 2, true,  'sad',   6],
    ['a', 2, false, 'happy', 7],
    ['a', 2, false, 'sad',   8],
    ['b', 1, true,  'happy', 9],
    ['b', 1, true,  'sad',   10],
    ['b', 1, false, 'happy', 11],
    ['b', 1, false, 'sad',   12],
    ['b', 2, true,  'happy', 13],
    ['b', 2, true,  'sad',   14],
    ['b', 2, false, 'happy', 15],
    ['b', 2, false, 'sad',   16]
  ]
)

Create a new instance. The first arg is an array of columns. Helps you see what you are inputing. The second arg is the table. It is an array of rows. Just fill it up with all the permutations of values that you need to decide on. The last value is the return value for a match.

table.decide(['b', 2, true, 'happy'], function (err, category) {
  t.equal(category, 13, 'we get the correct category')
})

Run a match on the table.

Much easier on the eyes then a bunch of if or switch stmts.

objects

Because the column names have been defined, you can also run a decision on an object. eg

var person = {
  first: 'Ryan',
  last: 'Ramage',
  type: 'b',
  count: 2,
  applied: true,
  emotion: 'happy'
}

table.decide(person, function (err, category) {
  t.equal(category, 13, 'we get the correct category')
})

Persist

The table uses levelup, with a default memdown backing. So you could swap out to a persistant store for very large tables.