This is a modern TypeScript port of the expr-eval library, completely rewritten with contemporary build tools and development practices. Originally based on expr-eval 2.0.2, this version has been restructured with a modular architecture, TypeScript support, and comprehensive testing using Vitest.
Parses and evaluates mathematical expressions. It's a safer and more math-oriented alternative to using JavaScript's eval function for mathematical expressions.
It has built-in support for common math operators and functions. Additionally, you can add your own JavaScript functions. Expressions can be evaluated directly, or compiled into native JavaScript functions.
npm install @pro-fa/expr-evalconst Parser = require('@pro-fa/expr-eval').Parser;
const parser = new Parser();
let expr = parser.parse('2 * x + 1');
console.log(expr.evaluate({ x: 3 })); // 7
// or
Parser.evaluate('6 * x', { x: 7 }) // 42| Document | Description |
|---|---|
| Parser | Parser class API, constructor options, and methods |
| Expression | Expression object methods: evaluate, substitute, simplify, variables, symbols, toString, toJSFunction |
| Expression Syntax | Operator precedence, unary operators, pre-defined functions, string manipulation, array literals, function definitions, constants |
| TypeScript Port Enhancements | New features: undefined support, coalesce operator, optional chaining, SQL case blocks, object construction, promises, and more |
| Language Service | IDE integration: code completions, hover information, syntax highlighting, Monaco Editor integration |
| Performance Testing | Benchmarks, performance grades, and optimization guidance |
- Mathematical Expressions - Full support for arithmetic, comparison, and logical operators
- Built-in Functions - Trigonometry, logarithms, min/max, array operations, string manipulation
- Custom Functions - Add your own JavaScript functions
- Variable Support - Evaluate expressions with dynamic variable values
- Expression Compilation - Convert expressions to native JavaScript functions
- TypeScript Support - Full type definitions included
- Undefined Support - Graceful handling of undefined values
- Coalesce Operator -
??operator for null/undefined fallback - SQL Case Blocks - SQL-style CASE/WHEN/THEN/ELSE expressions
- Object Construction - Create objects and arrays in expressions
- Language Service - IDE integration with completions, hover info, and highlighting
Try out the expression evaluator and its language server capabilities directly in your browser at the Playground. The playground provides an interactive environment with:
- Live expression evaluation
- Code completions and IntelliSense
- Syntax highlighting
- Hover information for functions and variables
cd <project-directory>
npm install
npm test# Run all benchmarks
npm run bench
# Run specific categories
npm run bench:parsing # Parser performance
npm run bench:evaluation # Evaluation performance
npm run bench:memory # Memory usageSee docs/performance.md for detailed performance documentation.
See LICENSE.txt for license information.