Working with JSON tables in TypeScript

Updated May 9, 2026

JSON file handling with automatic format detection and high-performance data operations.

Installation

npm install fairspec

Getting Started

The JSON plugin provides:

loadJsonTable - Load JSON files into tables
saveJsonTable - Save tables to JSON files
JsonPlugin - Plugin for framework integration

For example:

import { loadJsonTable } from "fairspec"

const table = await loadJsonTable({ data: "table.json" })
// Standard JSON array of objects format

Basic Usage

Loading JSON Files

import { loadJsonTable } from "fairspec"

// Load from local file
const table = await loadJsonTable({ data: "data.json" })

// Load from remote URL
const table = await loadJsonTable({
  data: "https://example.com/data.json",
})

// Load multiple files (concatenated)
const table = await loadJsonTable({
  data: ["file1.json", "file2.json"],
})

Saving JSON Files

import { saveJsonTable } from "fairspec"

// Save with default options
await saveJsonTable(table, { path: "output.json" })

// Save with explicit format
await saveJsonTable(table, {
  path: "output.json",
  format: { name: "json" },
})

Standard Format

JSON tables use an array of objects format:

[
  { "id": 1, "name": "Alice", "age": 30 },
  { "id": 2, "name": "Bob", "age": 25 }
]

Advanced Features

JSON Pointer Extraction

Extract data from nested objects using jsonPointer:

// Input: {"users": [{"id": 1, "name": "Alice"}]}
const table = await loadJsonTable({
  data: "data.json",
  format: {
    name: "json",
    jsonPointer: "users",
  },
})

Column Selection

Select specific columns using columnNames:

// Only load specific columns
const table = await loadJsonTable({
  data: "data.json",
  format: {
    name: "json",
    columnNames: ["name", "age"],
  },
})

Array Format Handling

Handle CSV-style array data with rowType: "array":

// Input: [["id", "name"], [1, "Alice"], [2, "Bob"]]
const table = await loadJsonTable({
  data: "data.json",
  format: {
    name: "json",
    rowType: "array",
  },
})

Saving with JSON Pointer

Wrap data in a nested structure when saving:

// Output: {"users": [{"id": 1, "name": "Alice"}]}
await saveJsonTable(table, {
  path: "output.json",
  format: {
    name: "json",
    jsonPointer: "users",
  },
})

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