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JSON: validation, schemas and working with large files

7 min read

2026-03-07

Advanced work with JSON: JSON Schema, JSONPath, jq queries, processing large files and API responses.

Advanced work with JSON

JSON Schema - structure validation

JSON Schema allows you to set rules for structure and data types:

{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "type": "object",
  "required": ["name", "age"],
  "properties": {
    "name": { "type": "string", "minLength": 1 },
    "age": { "type": "integer", "minimum": 0, "maximum": 150 },
    "email": { "type": "string", "format": "email" }
  }
}

JSONPath - data navigation

JSONPath is an analogue of XPath for JSON:

ExpressionMeaning
`$.store.book[*].author`All book authors
`$..price`All prices (recursive)
`$.book[?(@.price < 10)]`Books cheaper than 10
`$.book[-1:]`Last book

Working with large JSON files

For files over 10 MB, use streaming parsing:

**Node.js (stream-json):**

const { parser } = require('stream-json');
const { streamValues } = require('stream-json/streamers/StreamValues');

fs.createReadStream('large.json')
  .pipe(parser())
  .pipe(streamValues())
  .on('data', ({ value }) => processItem(value));

Common errors in JSON

1.

**Trailing comma** - extra comma at the end of the array/object

2.

**Single quotes** - JSON requires double quotes

3.

**undefined** - is not a valid JSON value

4.

**NaN/Infinity** - not supported, replace with null

Minification vs formatting

API best practices

•

Always return Content-Type: application/json

•

Use camelCase for keys in JavaScript API

•

Wrap collections: `{"data": [...], "meta": {...}}`

•

Version the API: `/api/v1/resource`

Format and validate JSON in JSON Formatter.

See also: YAML ↔ JSON, XML Formatter, Test Data Generator

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