JSONとは？

JSON (JavaScript Object Notation) is a lightweight, text-based data interchange format that uses human-readable key-value pairs and arrays to represent structured data. It is the dominant format for web APIs and configuration files.

What is JSON?

JSON (JavaScript Object Notation) is a data format that represents structured information as text using two fundamental structures: objects (collections of key-value pairs enclosed in curly braces) and arrays (ordered lists enclosed in square brackets). Values can be strings, numbers, booleans, null, objects, or arrays, allowing JSON to represent complex nested data structures.

Originally derived from JavaScript syntax, JSON is language-independent and supported by virtually every modern programming language. Its simplicity, readability, and universality have made it the de facto standard for data exchange in web applications, APIs, and configuration systems.

JSON in Data Extraction

JSON is central to modern data extraction workflows:

API responses: Most REST and GraphQL APIs return data in JSON format. Extracting data from an API means parsing JSON responses.

Web page data: Many websites embed data in JSON structures within their HTML — <script type="application/ld+json"> blocks, JavaScript variables, or inline data attributes. Extracting this embedded JSON is often more reliable than parsing HTML elements.

AJAX payloads: Single-page applications load data via asynchronous JavaScript calls that return JSON. Intercepting these network requests can be more efficient than scraping the rendered DOM.

Export formats: Many applications offer JSON as a data export option, providing a structured alternative to CSV.

JSON vs. Other Data Formats

JSON vs. CSV: CSV is simpler and works well for flat tabular data. JSON handles nested and hierarchical data that CSV cannot represent without workarounds. CSV is more compact for large flat datasets; JSON is more expressive.

JSON vs. XML: XML was the dominant data interchange format before JSON. XML is more verbose, supports attributes and namespaces, and has a schema validation ecosystem (XSD). JSON is lighter weight, easier to parse, and has become the preferred format for web APIs.

JSON vs. YAML: YAML is a superset of JSON that adds features like comments, multi-line strings, and references. YAML is preferred for configuration files; JSON for data interchange.

Working with JSON

When processing JSON in data pipelines, key operations include:

Parsing: Converting a JSON string into a native data structure (object, dictionary, hash map).

JSONPath / JQ queries: Extracting specific values from nested structures using query expressions (similar to XPath for XML).

Validation: Checking JSON data against a JSON Schema to ensure it meets expected structure and type requirements.

Transformation: Reshaping JSON structures — flattening nested objects, renaming keys, filtering arrays, or converting to tabular format for database loading.

なぜ重要か

JSON is the lingua franca of modern data exchange. Understanding JSON is essential for anyone working with APIs, web scraping, or data integration, as most data sources and tools communicate using this format.

Autonolyのソリューション

Autonoly handles JSON natively throughout its workflows. When extracting data from APIs or websites, the AI agent automatically parses JSON responses, extracts the relevant fields, and can transform the data into spreadsheets, databases, or other formats.

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例

Parsing JSON responses from a weather API to extract daily forecasts for a dashboard
Extracting product data from embedded JSON-LD structured data on e-commerce pages
Converting a nested JSON export from a project management tool into a flat CSV for spreadsheet analysis

よくある質問

What is the difference between JSON and a JavaScript object?

JSON is a text-based data format with strict syntax rules: keys must be double-quoted strings, no trailing commas, no comments, no functions. A JavaScript object is a runtime data structure that can contain functions, use unquoted keys, and include features not allowed in JSON. JSON is a serialization format; JavaScript objects are in-memory data structures. JSON.parse() converts JSON text to a JavaScript object, and JSON.stringify() does the reverse.

When should I use JSON vs. CSV for data storage?

Use CSV for flat, tabular data (rows and columns) where simplicity and file size matter — spreadsheet exports, database table dumps, or data meant for Excel. Use JSON when your data has nested or hierarchical structures, mixed data types, or when you need to preserve the relationship between parent and child records. JSON is also better for configuration files and API data exchange.

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