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.

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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

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Installation

npm install safe-expr-eval

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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

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Direct Evaluation

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

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

console.log(result); // 20

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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

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Supported Operations

Arithmetic

+  -  *  /  %

Comparison

==  !=  >  <  >=  <=

Logical

and  or  not
&&   ||   !

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Data Types

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

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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

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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

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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

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Standalone Functions

evaluate

evaluate(expression, variables?)

compile

compile(expression)

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Testing

npm test

npm run test:coverage

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License

MIT

See the LICENSE file for details.

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Contributing

Pull requests and contributions are welcome.

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Issues

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

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Author

Alejandro Castrillon

GitHub: https://github.com/