condition-flags-parser
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1.0.1 • Public • Published

JS Condition Parser

Parse/Apply JS-like condition expressions on an object of flags.

Purpose

Easily apply a JS logic condition string based on an array of flags. E.g.: bunch of flags (traits) of a user fetched from a fast backend (e.g. redis). Requested entity requires a bunch of flags with some logic (and, or, threshold) to apply.

Sample flags:
[
    'countryFlag:NL',
    'languageFlag:EN',
    'proUser'
]
Sample condition (logic):
proUser && (countryFlag:NL || languageFlag:NL)
Threshold example (two out of three):
proUser + countryFlag:NL + languageFlag:NL + !optedOut > 2

Support/requirements

Syntax
  • Parenthesis is supported
  • Valid operators (logic):
    • && (and)
    • || (or)
  • Valid threshold operators:
    • + (add)
    • - (subtract)
  • Valid comparison operators (for thresholds):
    • > (gt)
    • < (lt)
  • Invert
    • ! (not, e.g. flag does not apply, !someFlag)
Flags
  • Flags can contain these characters:
    • a-z
    • A-Z
    • 0-9
    • _ (underscore)
    • : (colon)
    • . (dot)
  • Flags must start with a-z or A-Z.
  • Flags should be present in the condition in plain texts (so no quotes surrounding them)
  • Flags are case sensitive

Use

import { validate, flags, apply } from 'condition-flags-parser'

const condition = '(someFlag:123 + anotherFlag) + (countryFlag:NL + !countryFlag:GB) > 3'

// 2nd argument = throw Error in case of validation Error
// Boolean, true if valid, or Throws
console.log(validate(condition, true))

// List flags the condition is working with (for e.g. redis `smismember`)
console.log(flags(condition))

// Returns boolean (condition applies?)
console.log(apply(condition, [
  'someFlag:123',
  'countryFlag:NL',
  'countryFlag:GB',
  'anotherFlag',
]))

Development

Tests: npm run test

Readme

Keywords

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Install

npm i condition-flags-parser

Weekly Downloads

1

Version

1.0.1

License

MIT

Unpacked Size

7.35 kB

Total Files

6

Last publish

Collaborators

  • wietsewind