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Core tier. Semver at 1.0: nothing breaks without a major release. See product tiers.

Overview

@bpmnkit/feel implements the FEEL expression language used in DMN decision tables and BPMN condition expressions, and passes 1,941 of the 2,053 FEEL cases in the DMN TCK (94.5%) — the remaining cases are listed with their reasons in tests/tck.test.ts. It implements Camunda 8's extensions to FEEL too, and matches 375 of the 378 runnable examples in Camunda's FEEL documentation (tests/camunda-parity.test.ts). It includes a tokenizer, recursive-descent parser, AST evaluator, formatter, and syntax highlighter.

Features

• Full FEEL grammar — arithmetic, comparisons, logic, function calls, paths, filters
• Temporal types — date, time, datetime, duration (ISO 8601, full spec compliance)
• Unary tests — DMN input expression syntax (> 5, "gold", "silver", [1..10])
• Built-in functions — 101 FEEL functions (string, list, numeric, date, context, range), including Camunda's extensions (assert, partition, to json, fromAi, …)
• Range expressions — [1..10], (0..1), [today..end]
• Context literals — { key: value, nested: { x: 1 } }
• Syntax highlighting — semantic token classification for editors
• Zero dependencies

Installation

npm install @bpmnkit/feel

Quick Start

Evaluate an expression

import { parseExpression, evaluate } from "@bpmnkit/feel"

const parsed = parseExpression("amount * 1.2 + fee")
if (!parsed.errors.length) {
  // `evaluate` takes an EvalContext — variables live under `vars`.
  const result = evaluate(parsed.ast!, { vars: { amount: 100, fee: 5 } })
  console.log(result) // 125
}

Evaluate unary tests (DMN input expressions)

import { parseUnaryTests, evaluateUnaryTests } from "@bpmnkit/feel"

// Does input value match any listed condition?
const parsed = parseUnaryTests('"gold","silver"')
const matches = evaluateUnaryTests(parsed.ast!, "gold", { vars: {} })
console.log(matches) // true

Syntax highlighting

import { annotate, highlightToHtml } from "@bpmnkit/feel"

// Classified tokens, for an editor to style itself.
annotate("x > 1")[0] // { kind: "variable", value: "x", start: 0, end: 1 }

// Or the same tokens already wrapped in <span class="feel-…"> elements.
highlightToHtml('if x > 10 then "high" else "low"')

API Reference

| Export | Description | |--------|-------------| | parseExpression(src) | Parse a FEEL expression → ParseResult | | parseUnaryTests(src) | Parse unary tests → ParseResult | | evaluate(ast, ctx) | Evaluate a parsed expression; ctx is { vars } | | evaluateUnaryTests(ast, input, ctx) | Test input against unary tests | | formatFeel(node, opts?) | Pretty-print a parsed node, not source text | | highlightToHtml(src) | Tokens wrapped in <span class="feel-…"> elements | | highlightFeel(src) | Alias for highlightToHtml | | tokenize(src) | Raw token stream | | annotate(src) | Tokens classified for highlighting (kind, value, start, end) |

ParseResult

interface ParseResult {
  ast: FeelNode | null
  errors: ParseError[]   // { message, start, end }
}

Related Packages

| Package | Description | |---------|-------------| | @bpmnkit/core | BPMN/DMN/Form parser, builder, layout engine | | @bpmnkit/canvas | Zero-dependency SVG BPMN viewer | | @bpmnkit/editor | Full-featured interactive BPMN editor | | @bpmnkit/engine | Lightweight BPMN process simulator for tests and demos | | @bpmnkit/plugins | 34 composable canvas plugins | | @bpmnkit/api | Camunda 8 REST API TypeScript client | | @bpmnkit/ascii | Render BPMN diagrams as Unicode ASCII art | | @bpmnkit/markdown | BPMN diagrams in Markdown — remark, markdown-it and README pre-rendering | | @bpmnkit/docspack | BPMN Kit docs as an offline docspack package for AI agents | | @bpmnkit/camunda-docspack | Camunda 8 docs as an offline docspack package for AI agents | | @bpmnkit/ui | Shared design tokens and UI components | | @bpmnkit/profiles | Shared auth, profile storage, and client factories for CLI & proxy | | @bpmnkit/operate | Monitoring & operations frontend for Camunda clusters | | @bpmnkit/connector-gen | Generate connector templates from OpenAPI specs | | @bpmnkit/connectors | Camunda 8 OOTB connector catalog and deterministic template application | | @bpmnkit/cli | Camunda 8 command-line interface (casen) | | @bpmnkit/proxy | Local AI bridge and Camunda API proxy server | | @bpmnkit/patterns | Domain process patterns for BPMNKit AIKit | | @bpmnkit/reebe-wasm | WebAssembly BPMN engine for browser simulation | | @bpmnkit/worker-client | Thin Zeebe REST client for standalone workers | | @bpmnkit/flow | Code-first durable flows that derive BPMN, job types and workers | | @bpmnkit/user-tasks | Embeddable user task widget for Camunda 8 | | @bpmnkit/cli-sdk | Plugin authoring SDK for the casen CLI | | @bpmnkit/create-casen-plugin | Scaffold a new casen CLI plugin in seconds | | @bpmnkit/casen-report | HTML reports from Camunda 8 incident and SLA data | | @bpmnkit/casen-worker-http | Example HTTP worker plugin — completes jobs with live JSONPlaceholder API data | | @bpmnkit/casen-worker-ai | AI task worker — classify, summarize, extract, and decide using Claude |

License

MIT © BPMN Kit — made by u11g