expjson

expjson

Super lightweight, fast, and optimized evaluate-able and compilable expressions in JSON written in TypeScript

Get Started

npm install -D expjson

or

yarn add -D expjson

How to Use

compileExpression and running it later is much faster if compiled expression is evaluated multiple times on many execution contexts.

evaluateExpression is faster if the expression is evaluated only once.

functionalities are exactly same for both.

import { compileExpression, evaluateExpression, IfThenElse, In, Not } from 'expjson';


evaluateExpression(
  // expression to evaluate
  [
    IfThenElse, // same as '?:'
    [In, 'admin', '$roles'], // test if "admin" is in "roles" context variable
    [Not, '$postDeleted'], // true if context variable "postDeleted" is false
    '$unauthorized', // context variable "unauthorized"
  ],
  // execution context
  {
    postDeleted: false,
    roles: ['user', 'admin'],
    unauthorized: 'Unauthorized Error',
  }
) === true


evaluateExpression(
  [
    '?:', // same as IfThenElse
    ['In', 'admin', '$roles'], // test if "admin" is in "roles" context variable
    ['!', '$postDeleted'], // true if context variable "postDeleted" is false
    '$unauthorized', // context variable "unauthorized"
  ],
  {
    postDeleted: true,
    roles: ['user', 'admin'],
    unauthorized: 'Unauthorized Error',
  }
) === false


evaluateExpression(
  [
    IfThenElse, // same as '?:'
    [In, 'admin', '$roles'], // test if "admin" is in "roles" context variable
    [Not, '$postDeleted'], // true if context variable "postDeleted" is false
    '$unauthorized', // context variable "unauthorized"
  ],
  {
    postDeleted: false,
    roles: ['user', 'guest'],
    unauthorized: 'Unauthorized Error',
  }
) === 'Unauthorized Error'


const compiled1 = compileExpression([
  IfThenElse, // same as '?:'
  [In, 'admin', '$roles'], // test if "admin" is in "roles" context variable
  [Not, '$postDeleted'], // true if context variable "postDeleted" is false
  '$unauthorized', // context variable "unauthorized"
]);

compiled1({
  postDeleted: false,
  roles: ['user', 'admin'],
  unauthorized: 'Unauthorized Error',
}) === true


const compiled2 = compileExpression([
  '?:', // same as IfThenElse
  ['In', 'admin', '$roles'], // test if "admin" is in "roles" context variable
  ['!', '$postDeleted'], // true if context variable "postDeleted" is false
  '$unauthorized', // context variable "unauthorized"
]);

compiled2({
  postDeleted: true,
  roles: ['user', 'admin'],
  unauthorized: 'Unauthorized Error',
}) === false


const compiled3 = compileExpression([
  IfThenElse, // same as '?:'
  [In, 'admin', '$roles'], // test if "admin" is in "roles" context variable
  [Not, '$postDeleted'], // true if context variable "postDeleted" is false
  '$unauthorized', // context variable "unauthorized"
]);

compiled3({
  postDeleted: false,
  roles: ['user', 'guest'],
  unauthorized: 'Unauthorized Error',
}) === 'Unauthorized Error'

License

MIT License