One search. Connected ideas.

Understand the runtime and build reliable HTTP APIs.

Node.js is a JavaScript runtime designed to handle many operations that spend time waiting for I/O. It lets the operating system and supporting runtime facilities wait for work, then runs ready JavaScript callbacks on an event-loop thread. This makes one process useful for many concurrent connections without one JavaScript thread per request.

Backpressure is a feedback mechanism that slows a producer when the consumer cannot keep up. Without it, incoming chunks may accumulate in memory even though the application is using streams. Node streams expose flow-control signals and utilities that help coordinate reading, writing, cleanup and errors.

The event loop is the scheduling mechanism that decides when ready callbacks can run. Node organizes several categories of callbacks into phases, with separate processing for promise microtasks and next-tick callbacks. A timer delay is a minimum waiting threshold, not a promise of an exact execution time.

A process is an independently running program with its own address space and operating-system resources. A worker thread is another execution thread inside a process; Node workers have separate JavaScript execution environments and can exchange messages or share selected memory. Workers help CPU parallelism, while processes also provide stronger failure isolation.

A buffer is a container for raw bytes, while a stream processes a sequence of data in chunks. EventEmitter is a mechanism for registering listeners and notifying them when an event occurs. These tools work together in Node networking and file handling, where data can arrive gradually.

V8 is the engine that executes JavaScript, while libuv provides the event loop and cross-platform I/O support. The libuv thread pool runs certain operations that would otherwise block, such as many file-system calls. These are separate roles: V8 does not itself manage every network request, and not every async call uses a pool thread.

CommonJS and ES Modules are two systems for dividing JavaScript code into reusable modules. CommonJS uses runtime require calls, while ES Modules provide standard import and export declarations with a statically described dependency structure. Their loading and interoperability rules depend on the runtime and file configuration.

An HTTP status code describes the outcome of an HTTP request using a standard numeric category. Clients use it to decide whether to use a result, correct a request, authenticate or retry. A response body can add application details, but should not contradict the status code.

PUT is defined around creating or replacing the state of a target resource, while PATCH applies a described partial change. Idempotency means repeating an identical operation has the same intended server-side effect as doing it once. It does not require every repeated response to contain the same status or body.

HTTP versions preserve the basic request/response model but change how messages travel over the network. HTTP/2 multiplexes streams over one TCP connection, while HTTP/3 uses QUIC to avoid some transport-level blocking between streams. These improvements affect connection efficiency, not the need for correct API semantics.

A cookie is a small piece of browser-managed data sent automatically with matching requests. A server-side session uses an unpredictable identifier, often in a cookie, to look up login state on the server. This lets the server revoke or change that state without placing all session details in the browser.

CORS is a browser-enforced protocol that lets a server permit selected cross-origin response access. The browser checks response headers and may send a preflight request before the actual request. It is not a firewall: clients outside the browser can still call the API, and some cross-origin requests can be sent even without readable responses.

The event loop is the scheduling mechanism that decides when ready callbacks can run. Node organizes several categories of callbacks into phases, with separate processing for promise microtasks and next-tick callbacks. A timer delay is a minimum waiting threshold, not a promise of an exact execution time.

Backpressure is a feedback mechanism that slows a producer when the consumer cannot keep up. Without it, incoming chunks may accumulate in memory even though the application is using streams. Node streams expose flow-control signals and utilities that help coordinate reading, writing, cleanup and errors.

Node.js is a JavaScript runtime designed to handle many operations that spend time waiting for I/O. It lets the operating system and supporting runtime facilities wait for work, then runs ready JavaScript callbacks on an event-loop thread. This makes one process useful for many concurrent connections without one JavaScript thread per request.

A process is an independently running program with its own address space and operating-system resources. A worker thread is another execution thread inside a process; Node workers have separate JavaScript execution environments and can exchange messages or share selected memory. Workers help CPU parallelism, while processes also provide stronger failure isolation.

A buffer is a container for raw bytes, while a stream processes a sequence of data in chunks. EventEmitter is a mechanism for registering listeners and notifying them when an event occurs. These tools work together in Node networking and file handling, where data can arrive gradually.

V8 is the engine that executes JavaScript, while libuv provides the event loop and cross-platform I/O support. The libuv thread pool runs certain operations that would otherwise block, such as many file-system calls. These are separate roles: V8 does not itself manage every network request, and not every async call uses a pool thread.

CommonJS and ES Modules are two systems for dividing JavaScript code into reusable modules. CommonJS uses runtime require calls, while ES Modules provide standard import and export declarations with a statically described dependency structure. Their loading and interoperability rules depend on the runtime and file configuration.

An HTTP status code describes the outcome of an HTTP request using a standard numeric category. Clients use it to decide whether to use a result, correct a request, authenticate or retry. A response body can add application details, but should not contradict the status code.

PUT is defined around creating or replacing the state of a target resource, while PATCH applies a described partial change. Idempotency means repeating an identical operation has the same intended server-side effect as doing it once. It does not require every repeated response to contain the same status or body.

HTTP versions preserve the basic request/response model but change how messages travel over the network. HTTP/2 multiplexes streams over one TCP connection, while HTTP/3 uses QUIC to avoid some transport-level blocking between streams. These improvements affect connection efficiency, not the need for correct API semantics.

A cookie is a small piece of browser-managed data sent automatically with matching requests. A server-side session uses an unpredictable identifier, often in a cookie, to look up login state on the server. This lets the server revoke or change that state without placing all session details in the browser.

CORS is a browser-enforced protocol that lets a server permit selected cross-origin response access. The browser checks response headers and may send a preflight request before the actual request. It is not a firewall: clients outside the browser can still call the API, and some cross-origin requests can be sent even without readable responses.

Node.js learning module

Node.js learning module

Node.js learning module

Node.js learning module