safe-expr-eval

Fast and lightweight expression evaluator for JavaScript and TypeScript.

A modern expression parser with a familiar API, zero dependencies, and full TypeScript support.

Features

• Fast expression parsing and evaluation
• Lightweight and dependency-free
• Full TypeScript support
• Simple and familiar API
• Custom functions and constants
• ES2020+ compatible
• Well tested

Installation

npm install safe-expr-eval

Quick Start

Basic Usage

import { Parser } from 'safe-expr-eval';

const parser = new Parser();
const expr = parser.parse('2 * x + 1');

console.log(expr.evaluate({ x: 3 })); // 7
console.log(expr.evaluate({ x: 10 })); // 21

Direct Evaluation

import { evaluate } from 'safe-expr-eval';

const result = evaluate('10 + 5 * 2');

console.log(result); // 20

Compiled Expressions

import { compile } from 'safe-expr-eval';

const fn = compile('price * quantity * (1 - discount)');

console.log(
  fn({
    price: 100,
    quantity: 2,
    discount: 0.1
  })
); // 180

Supported Operations

Arithmetic

+  -  *  /  %

Comparison

==  !=  >  <  >=  <=

Logical

and  or  not
&&   ||   !

Data Types

Numbers   → 42, 3.14
Strings   → "hello"
Booleans  → true, false
Variables → price, user.name

Custom Functions

const parser = new Parser();

parser.functions.max = Math.max;
parser.functions.min = Math.min;
parser.functions.round = Math.round;

const expr = parser.parse(
  'round(max(a, b) * 1.5)'
);

console.log(
  expr.evaluate({
    a: 10,
    b: 20
  })
); // 30

Constants

const parser = new Parser();

parser.consts.PI = Math.PI;
parser.consts.TAX_RATE = 0.15;

const expr = parser.parse(
  'price * (1 + TAX_RATE)'
);

console.log(
  expr.evaluate({
    price: 100
  })
); // 115

API

Parser

Create parser

new Parser()

Parse expression

parser.parse(expression)

Evaluate expression

parser.evaluate(expression, variables?)

Functions registry

parser.functions

Constants registry

parser.consts

Standalone Functions

evaluate

evaluate(expression, variables?)

compile

compile(expression)

Testing

npm test

npm run test:coverage

License

MIT

See the LICENSE file for details.

Contributing

Pull requests and contributions are welcome.

Issues

Please open an issue if you find a bug or have a feature request.

Author

Alejandro Castrillon

GitHub: https://github.com/