Common Expression Language (CEL) evaluator for JavaScript
npm install cel-jscel-js is a powerful and efficient parser and evaluator for Google's Common Expression Language (CEL), built on the robust foundation of the Chevrotain parsing library. This library aims to provide a seamless and easy-to-use interface for working with CEL in JavaScript environments.
Try out cel-js in your browser with the live demo.
- 🚀 Fast and Efficient Parsing: Leverages Chevrotain for high-performance parsing and evaluation
- 🌍 Isomorphic: Ready for server and browser
- 📦 ESM support
- 📚 Supported CEL Features:
- [x] Literals
- [x] int
- [x] uint
- [x] double
- [x] bool
- [x] string
- [x] single-quote string
- [x] double-quote string
- [ ] raw string
- [ ] triple-quote string
- [ ] byte string
- [x] hexadecimal
- [ ] bytes
- [x] list
- [x] map
- [x] null
- [x] Conditional Operators
- [x] Ternary (condition ? true : false)
- [x] Logical And (&&)
- [x] Logical Or (||)
- [x] Equality Operators (==, !=)
- [x] Relational Operators (<, <=, >, >=, in)
- [x] Arithmetic Operators (+, -, *, /, %)
- [x] Identifiers
- [x] Dot Notation (foo.bar)
- [x] Index Notation (foo["bar"])
- [x] Macros: (has, size, etc.)
- [x] All (e.all(x, p))
- [x] Exists (e.exists(x, p))
- [x] Exists one (e.exists_one(x, p))
- [x] Filter (e.filter(x, p))
- [x] Has (has(foo.bar))
- [x] Map (e.map(x, t) and e.map(x, p, t))
- [x] Size (size(foo))
- [x] Unary Operators (!true, -123)
- [x] Custom Functions (myFunction())
- [x] Comments (// This is a comment)
To install cel-js, use npm:
``bash`
npm i cel-js
evaluate is the primary function for parsing and evaluating CEL expressions. It takes an expression string and an optional object of variables to use in the expression.
`ts
import { evaluate, parse } from 'cel-js'
// use evaluate to parse and evaluate an expression
evaluate('2 + 2 * 2') // => 6
evaluate('"foo" + "bar"') // => 'foobar'
evaluate('user.role == "admin"', { user: { role: 'admin' } }) // => true
`
parse is a lower-level function that only parses an expression string into an AST. This can be useful if you want to evaluate the expression multiple times with different variables or if you want to validate the syntax of an expression.
`tsparse
// use to parse an expression, useful for validation purposes
const result = parse('2 + a')
if (!result.isSuccess) {
// your business logic
}
// you can reuse the result of parse to evaluate the expression``
evaluate(result.cst, { a: 2 }) // => 4
evaluate(result.cst, { a: 4 }) // => 6
- Errors types and messages are not 100% consistent with the cel-go implementation,