Definitions beginning with J

JAMstack

Architecture approach based on JavaScript, APIs and prebuilt files, often distributed through a CDN.

In practice: Check how content, forms and updates work after generation.

Java

General-purpose programming language used for many systems, services and enterprise applications.

In practice: Check the version required by the project and its dependencies before planning an update.

JavaScript

Programming language used in browsers and other environments, including servers. It can handle events, calculations and network exchanges. The language and its environment’s APIs are distinct: a capability available in a browser is not automatically available on a server.

Reference: MDN : JavaScript · Source consulted 2026-10-18

In practice: check what remains usable before the script runs and when it fails.

JavaScript rendering

Producing or changing page content with browser JavaScript. Distinguish initial HTML from subsequently created content, and test waiting, script failure and actions before loading finishes.

Reference: MDN : How browsers work · Source consulted 2026-10-18

In practice: Compare initial HTML with the rendered page to see whether essential information remains available.

JPEG

A raster image format commonly used for photographs with lossy compression. Fine detail can deteriorate, and conventional JPEG does not preserve an alpha transparency channel.

Reference: MDN : Image formats · Source consulted 2026-10-18

In practice: Compare quality and file size on a real photo before choosing compression.

jQuery

Long-standing JavaScript library simplifying document manipulation, events and certain network requests.

In practice: Find its actual uses before keeping or removing it from an existing site.

JSON

Text interchange format representing objects, arrays, strings, numbers, booleans and null. Its syntax requires double-quoted property names. Parseable JSON still needs checks against expected structure and types; it is not executed as a program.

Reference: MDN : JSON · Source consulted 2026-10-18

In practice: Validate expected structure and types before consuming an external response.

JSON Schema

Vocabulary for describing JSON structure and constraints, then checking data with a compatible validator. Declare the schema version and required fields. Structural validation establishes neither factual accuracy nor permission to perform an operation.

Reference: JSON Schema : Overview · Source consulted 2026-10-18

In practice: Validate valid and invalid examples, then evolve the schema with real data.

JSON-LD

JSON format for linked data, often used to embed Schema.org structured data in a page. The context gives keys and identifiers their meaning. Validating JSON alone does not verify the relationships between described entities.

Reference: W3C · JSON-LD 1.1 · Source consulted 2026-10-25

In practice: Compare declared data with visible content, then validate the graph after rendering.

JWT

Compact claims format, signed or encrypted depending on its form. Decoding is insufficient: verify cryptographic protection, issuer, audience and validity.

Reference: IETF · RFC 7519 · JSON Web Token · Source consulted 2026-10-31

Source consulted : IETF · RFC 8725 · JWT Best Current Practices · 2026-10-31

In practice: Check signature, validity period and intended audience before accepting a token.