katex-ui

Framework-free formula engine and schema toolkit for dynamic calculators.

katex-ui owns the durable domain layer: expression validation, LaTeX conversion, variable extraction, serializable calculator config, schema normalization, batch calculation, reusable runners, and display-safe formatting.

It is not a TeX renderer like katex: use it when formulas need to become calculator schemas, live forms, and persisted business rules.

Install

pnpm add katex-ui

Repository

github.com/LaoChen1994/katex-ui

Homepage

laochen1994.github.io/katex-ui/

Highlights

• Formula engine - calculate arithmetic expressions with variables and functions.
• LaTeX bridge - convert \frac, \sqrt, powers, functions, and simple subscripts.
• Schema generator - turn variables into stable FormulaSchema fields.
• Calculator config - serialize source, expression, fields, and result metadata.
• Batch formulas - derive ordered values such as subtotal, tax, and total.
• Renderer agnostic - no React, Vue, or form-renderer runtime dependency.

Quick Start

import { createLatexFormulaCalculator } from 'katex-ui/parser';

const calculator = createLatexFormulaCalculator({
  source: '\\frac{price \\times count}{discount}',
  fields: [
    { name: 'price', label: 'Price', defaultValue: 100 },
    { name: 'count', label: 'Count', defaultValue: 2 },
    { name: 'discount', label: 'Discount', defaultValue: 4 },
  ],
  result: {
    label: 'Total',
    precision: 12,
  },
});

calculator.config;
calculator.schema;
calculator.calculate({ price: 100, count: 2, discount: 4 });
// { value: 50, errors: [] }

API Surface

• katex-ui/core - calculateFormula, createFormulaRunner, calculateFormulaBatch, formatFormulaValue.
• katex-ui/parser - latexToExpression, parseLatexFormula, createLatexFormulaCalculator.
• katex-ui/schema - createFormulaSchema, createFormulaCalculatorConfig, mergeFormulaFields.

Quality

• Unit tests: 46 core/parser/schema tests.
• Coverage: 90.37% statements, 83.55% branches, 96% functions.
• Build: tsup ESM + .d.ts.
• Runtime dependencies: none.