logical-compiler

Compile MongoDB-like boolean expressions based on boolean operators AND and OR

Installation

Use one of the two based on your project's dependency manager.

$ npm install logical-compiler --save

$ yarn add logical-compiler

Getting started

import compile from 'logical-compiler';

compile(expression, options); // false

Arguments:

• expression - the boolean expression to be executed.
• options - an optional object specifying options.
  • fns - an optional attribute specifying any function(s) used on the expression.

Operators

AND operator

let expression = { $and: [true, true] };
compile(expression); // true

expression = { $and: [true, false] };
compile(expression); // false

expression = { $and: [false, true] };
compile(expression); // false

expression = { $and: [false, false] };
compile(expression); // false

OR operator

let expression = { $or: [true, true] };
compile(expression); // true

expression = { $or: [true, false] };
compile(expression); // true

expression = { $or: [false, true] };
compile(expression); // true

expression = { $or: [false, false] };
compile(expression); // false

Unrecognized operator

const expression = { $someOp: ['x', 'y'] };

compile(expression); // Error: Unrecognized operator: '$someOp'

Primitives

undefined

compile(); // Error: Expected an expression

boolean

compile(true); // true

compile(false); // false

string

const expression = 'test';

compile(expression); // Error: Unexpected token 'test'

number

const expression = 201;

compile(expression); // Error: Unexpected token '201'

Callbacks

Simple callback

let cb = () => true;
compile(cb); // true

cb = () => false;
compile(cb); // false

Promise callback

cb = () => Promise.resolve(true);
await compile(cb); //true

cb = () => Promise.resolve(false);
await compile(cb); // false

Nested promise callback

const expression = {
  $and: [true, () => Promise.resolve(true)],
};

compile(expression); // Error: Unexpected nested promise callback

Functions

Simple function

const options = {
  fns: {
    isEven: (number) => number % 2 === 0,
  },
};

let expression = { isEven: 7 };
compile(expression, options); // false

expression = { isEven: 6 };
compile(expression, options); // true

Note that the function is defined on the fns attribute of the options argument.

Promise function

const options = {
  fns: {
    isEqual: (num1, num2) => Promise.resolve(num1 === num2),
  },
};

expression = { isEqual: [3, 3] };
await compile(expression, options); // true

expression = { isEqual: [3, 5] };
await compile(expression, options); // false

Nested promise function

const options = {
  fns: {
    authenticated: () => Promise.resolve(true),
  },
};

const expression = {
  $or: [false, { authenticated: null }],
};

compile(expression, options); // Error: Unexpected nested promise function

Undefined function

const expression = { someFn: ['x', 'y'] };

compile(expression, options); // Error: Undefined function: 'someFn'

Compound expressions

let expression = {
  $or: [{ $and: [true, true] }, false],
};

compile(expression); // true

expression = {
  $or: [() => false, () => false],
};

compile(expression); // false

expression = {
  $and: [() => true, true],
};

compile(expression); // true

expression = {
  $or: [
    () => false,
    false,
    {
      $and: [true, { $or: [() => true, false] }],
    },
  ],
};

compile(expression); // true

const options = {
  fns: {
    any: (target, values) => values.includes(target),
    all: (targets, values) => targets.every((target) => values.includes(target)),
  },
};

expression = {
  $and: [
    () => true, 
    { $or: [true, false] },
    { any: [5, [1, 3, 4, 6, 7]] }
  ],
};

compile(expression, options); // false

expression = {
  $or: [
    () => false,
    false,
    { $and: [true, false] },
    {
      all: [
        [3, 4, 7],
        [2, 3, 4, 5, 6, 7],
      ],
    },
  ],
};

compile(expression, options); // true

Operators can be nested in any fashion to achieve the desired logical check.

IMPORTANT NOTES

1. An asynchronous call can be made inside a callback or function. Currently, the library does not support promise returning callbacks or functions on nested expressions. If one is found, an exception is thrown. Promise returning executables are only allowed ALONE. The clean workaround is to resolve values resulting from asynchronous calls before invoking the compiler.

2. Callbacks and functions must explicitly return boolean values to avoid the ambiguity of relying on truthiness. Relying on truthiness would pose a serious loophole because the executable might accidentally resolve to true on a non-boolean value. If the library encounters a callback that resolves to a non-boolean value, it throws an exception. See MDN documentation on truthy values.

Licence

MIT © Mutai Mwiti | GitHub | GitLab

DISCLAIMER: All opinions expressed in this repository are mine and do not reflect any company or organisation I'm involved with.