@jexs/core

The resolver engine and pure-logic nodes for Jexs — a JSON expression system where every UI, route, or value is just JSON, interpreted at runtime by typed Node classes.

This package is environment-agnostic (no DOM, no Node.js APIs) and is the foundation every other @jexs/* package builds on.

Part of Jexs.

Install

npm install @jexs/core

What's inside

Resolver — createResolver(nodes) returns a resolve(value, context) function that walks JSON, dispatches on object keys, and threads a per-call context. Sync-first: no Promise is created unless an async node actually appears in the tree.

Core nodes (coreNodes):

| Node | Keys | Purpose | |---|---|---| | VariablesNode | var, setVars | Read/write context by dot-path | | LogicNode | if, switch, foreach, and, or, not, eq, lt, gt, ... | Branching, iteration, comparisons | | ElementNode | tag | Render an HTML element tree to a string | | StringNode | concat, replace, split, trim, ... | String ops | | ArrayNode | map, filter, length, join, sort, ... | Array ops | | MathNode | sum, avg, min, max, clamp, random, ... | Numeric ops | | DateNode | now, date-format, date-add, ... | Dates | | TimerNode | setTimeout, setInterval, clearTimer | Timing | | ErrorNode | error | Throw { status, message } HTTP errors |

Quick example

import { createResolver, coreNodes } from "@jexs/core";

const resolve = createResolver(coreNodes);

const ctx = { user: { name: "Ada" } };

resolve({ concat: ["Hello, ", { var: "$user.name" }, "!"] }, ctx);
// → "Hello, Ada!"

resolve({
  if: { var: "$user.name" },
  then: { concat: ["Welcome back, ", { var: "$user.name" }] },
  else: "Sign in"
}, ctx);
// → "Welcome back, Ada"

Extending — write your own node

import { Node, type Context, createResolver, coreNodes } from "@jexs/core";

class UpperNode extends Node {
  upper(def: Record<string, unknown>, _ctx: Context) {
    return String(def.upper).toUpperCase();
  }
}

const resolve = createResolver([...coreNodes, new UpperNode()]);
resolve({ upper: "hello" }, {}); // → "HELLO"

The method name upper becomes the dispatch key — any JSON object with an upper field will route to that handler.

License

MIT