formulex

🧠 Formulex (Formula + Expression + Exec)

Formulex is a lightweight and extensible library that parses user-defined formulas into SQL expressions or executable JavaScript functions — with built-in AST support.

Perfect for low-code platforms, dashboards, calculated fields, and dynamic logic engines.

🚧 This project is a work in progress. Expect bugs and frequent updates.

🚀 Features

• ✅ Convert formulas like {Field 1} + {Field 2} * 2 into SQL
• ✅ Generate executable JavaScript functions from formulas
• ✅ Parse formulas into abstract syntax trees (AST)
• ✅ Support for custom field mappings and types
• ✅ Zero runtime dependencies

📦 Installation

npm install formulex

📗 Usage

import { Parser } from 'formulex';

const fields = [
  { id: '1', name: 'Field 1', type: 'number' },
  { id: '2', name: 'Field 2', type: 'number' },
];

const expression = '{Field_1} + {Field_2} * 2';

const parser = new Parser(expression, fields);

const sql = parser.toSqlWithVariables()
// => (123 + (321 * 2))

const jsFormula = parser.toJs();
// => VARIABLES["1"] + (VARIABLES["2"] * 2)

const result = parser.runJs(jsFormula, { 1: 10, 2: 5 });
// => 20

🛠 API

new Parser(expression: string, fields?: IField[], fieldAttribute?: keyof IField) Creates a new parser instance.

expression: your input formula (e.g. {Field 1} + 10)

fields: optional array of fields (with id, name, type)

fieldAttribute: defines how variables are resolved (id, name, etc.)

parser.toSqlWithVariables(): string Converts the formula into a valid SQL expression string.

parser.toJs(): string Returns a JS-compatible string (to be evaluated with new Function).

parser.runJs(js: string, values: Record<string, unknown>): unknown Executes a previously generated JS string with given values.

parser.getAst(): StatementsNode Returns the abstract syntax tree (AST) of the formula.

parser.walkAst(visitor: (node: Node) => void): void Traverses all nodes of the AST in depth-first order and invokes the visitor callback on each node. Useful for custom validation, metadata extraction, or modifying behavior. Supported node types: Number, Variable, BinaryExpression, CallExpression, UnaryExpression, etc.

parser.getVariables(): string[] Returns all unique variable names used in the formula.

🧮 Supported Operators

Type	Operators	Example
Arithmetic	+, -, *, /, %	{price} * {quantity} + 1
Comparison	==, !=, >, <, >=, <=	{amount} > 100
Logical	AND, OR, NOT	active == true AND score > 5
Grouping	Parentheses ( )	(a + b) * c
Variables	Dynamic keys from your data	user.age, order.total

🧩 Use Cases

• Dynamic calculated fields in dashboards or CRMs

• Low-code formula engines

• Report builders

• Pricing rules and financial modeling

• Serverless logic execution

📄 License

MIT