escalc is an opinionated NCalc expression evaluator in TypeScript. It exposes a parser, a tree-walk evaluator, a formatter, and a parameter extractor for a well-defined subset of the NCalc expression language.
Designed for a small footprint and fast execution with zero dependencies.
npm install @imogenz/escalc
# or
pnpm add @imogenz/escalc
# or
yarn add @imogenz/escalcimport { evaluate } from "@imogenz/escalc";
// Basic arithmetic
evaluate("1 + 2"); // => 3
evaluate("2 ** 8"); // => 256
evaluate("Max(Abs(-5), 2)"); // => 5
// Parameters
evaluate("[price] * (1 + [tax])", {
params: new Map([
["price", 100],
["tax", 0.2],
]),
}); // => 120
// Safe variant - no throwing
import { evaluateSafe } from "@imogenz/escalc";
const result = evaluateSafe(userInput);
if (result.type === "success") console.log(result.result);See the Demos guide for complete real-world examples.
Created using a recursive descent parser with a handwritten lexer and tree-walk evaluator.
The parser supports error recovery: with stopOnFirstError: false it collects all
recoverable errors and returns a partial AST via incompleteExpression.
| Feature | Status |
|---|---|
Arithmetic (+ - * / % **) |
✅ |
Comparison (> < >= <= == !=) |
✅ |
Logical (&& || !) with short-circuit |
✅ |
Bitwise (& | ^ << >> ~) |
✅ |
Ternary (? :) |
✅ |
in / not in |
✅ |
| String / number / boolean / date / list literals | ✅ |
Parameter references ([name], {name}) |
✅ |
| Built-in math functions (Abs, Sin, Sqrt, …) | ✅ |
if / ifs conditional functions |
✅ |
| Custom functions | ✅ |
| Lazy parameters | ✅ |
Custom operator implementation (Calculator) |
✅ |
| Result caching | ❌ won't implement - cache at call site |
| GUID value type | ❌ won't implement - use a string |
See Supported Features for the full reference.
| NCalc flag | ESCalc equivalent |
|---|---|
EvaluateOptions.IterateParameters |
Not supported |
EvaluateOptions.IgnoreCase |
Not supported - parameter names are case-sensitive |
EvaluateOptions.NoCache |
Default behaviour (no caching) |
EvaluateOptions.RoundAwayFromZero |
Override Calculator.modulus / Round |
| Custom function handler | functions option in evaluate / execute |
| Custom value factory | Extend StandardCalculator |
Override the provided Calculator interface or extend StandardCalculator to
change how operators work. Extend AbstractVisitor<T> for custom AST traversal.
See Overriding Evaluation for examples.