JSON Templates

A lightweight utility to substitute variables in strings, objects, and arrays. Built on top of json-templates, it adds smart stringification: objects injected into strings are automatically converted to JSON instead of [object Object].

Installation

npm install @bonniernews/json-templates

Usage

import { render } from "@bonniernews/json-templates";

const data = {
  admin: { id: 1, name: "Alice" },
  tags: ["security", "management"],
  meta: { lastLogin: "2023-10-01" }
};

const template = {
  // 1. Entire Object Substitution (Preserves Type)
  user: "{{admin}}",
  
  // 2. Array Indexing (Using dot notation)
  primaryTag: "{{tags.0}}",
  
  // 3. Smart Stringification (Automatic JSON inside strings)
  summary: "User {{admin.name}} with tags {{tags}} logged in at {{meta.lastLogin}}"
};

const result = render(template, data);

/*
result = {
  user: { id: 1, name: "Alice" }, // Becomes the raw object
  primaryTag: "security",         // Accesses first element
  summary: "User Alice with tags [\"security\",\"management\"] logged in at 2023-10-01"
}
*/

Features

• Deep Substitution: Recursively processes nested strings, objects, and arrays.
• Array Indexing: Access elements using dot notation (e.g., {{list.0}}).
• Smart Coercion: Objects placed inside a string (e.g. "val: {{obj}}") are automatically JSON stringified via a recursive Proxy.
• Type Preservation: If a template string is exactly {{myObj}}, it returns the original object/array type rather than a string.

API

render<T>(template: T, data: Record<string, any>): T

• template: The source string, object, or array to process.
• data: The variables to inject.
• Returns: The processed template with values substituted.

Acknowledgments

This library is a wrapper around the excellent json-templates by Mikael Brevik.

License

MIT