JavaScript Execution Model: Contexts, Realms, Jobs & Agents — Quiz

Check your understanding of ECMAScript execution contexts, Realms, Jobs, agents, and host boundaries.

Skip a hard question and review it before your results.

Questions and answer options can shuffle between attempts.

You can retake this quiz whenever you like.

Question 1 of 16

What does an execution context track?

Answer options A Runtime evaluation state and related execution metadata B Only CSS styles C Only DOM nodes D Only source-code comments

An execution context is a specification device for tracking runtime evaluation.

Question 2 of 16

Where is the running execution context found?

Answer options A At the top of the execution-context stack B In the DOM C Inside every object D Only inside a Promise

The running context is the top element of the execution-context stack.

Question 3 of 16

Can JavaScript directly access an Environment Record?

Answer options A No B Yes, through globalThis C Yes, through Reflect D Only in strict mode

Environment Records are specification mechanisms, not program-visible objects.

Question 4 of 16

What does the Realm component of an execution context identify?

Answer options A The Realm Record associated with the code B The current URL string C The current DOM element D The current Promise

The Realm component identifies the Realm Record from which associated code accesses ECMAScript resources.

Question 5 of 16

Why can two Realms have distinct intrinsic objects?

Answer options A Each Realm has its own ECMAScript intrinsic set B Because arrays are random C Because syntax changes D Because every function creates a Realm

A Realm provides its own intrinsic objects and associated ECMAScript resources.

Question 6 of 16

What is an ECMAScript Job?

Answer options A A computation scheduled to run when no other ECMAScript computation is in progress B A DOM event listener C A CSS task D A garbage-collection guarantee

Jobs initiate ECMAScript computation and are scheduled by the host in an agent.

Question 7 of 16

Can two Jobs be actively evaluated at once in one agent?

Answer options A No B Yes, always C Only for Promises D Only in strict mode

The specification permits only one actively evaluated Job at a time in an agent.

Question 8 of 16

What does “run to completion” mean for a Job?

Answer options A Another Job does not begin until the current Job finishes B The Job can never throw C The Job must finish within one millisecond D The host cannot observe it

Once Job evaluation starts, another Job cannot start until it finishes.

Question 9 of 16

Which is part of an agent?

Answer options A Execution contexts and their stack plus agent state and an executing thread B Only a Promise queue C Only a Realm D Only the DOM

An agent includes contexts, the stack, running context, Agent Record, and executing thread.

Question 10 of 16

Why does SharedArrayBuffer matter to the agent model?

Answer options A Agents can interact through shared memory under the ECMAScript memory model B It creates a new lexical grammar C It replaces Realms D It disables Jobs

Shared memory provides cross-agent communication subject to memory-model rules.

Question 11 of 16

What is an agent cluster?

Answer options A A specification-level grouping of agents used for shared-memory relationships B A JavaScript class C A DOM tree D A Promise subclass

Agent clusters describe relationships among agents, including shared-memory possibilities.

Question 12 of 16

What is forward progress?

Answer options A An agent eventually performs evaluation steps when it is unblocked B A Promise always resolves C A Realm changes URL D A function gains a prototype

The specification defines forward-progress requirements for unblocked agents.

Question 13 of 16

Why does ScriptOrModule state exist in an execution context?

Answer options A To identify the originating Script or Module during evaluation B To store CSS C To identify a DOM element D To store a Promise result

Execution contexts retain the Script or Module from which their code originated.

Question 14 of 16

What does a Promise callback illustrate?

Answer options A A callback can be invoked as part of a scheduled Job B Promises bypass execution contexts C Callbacks execute during parsing D Promises create new syntax

Promise reaction callbacks are evaluated through Jobs and execution contexts.

Question 15 of 16

Who supplies the concrete scheduling environment around ECMAScript Jobs?

Answer options A The host environment B The JavaScript parser only C The object prototype chain D The type system

ECMAScript specifies host hooks; hosts provide concrete scheduling behavior.

Question 16 of 16

What should a browser event-loop lesson own later?

Answer options A Browser-specific task/event-loop integration B Execution-context definitions C Private class fields D ArrayBuffer byte order

The browser phase owns host-specific event-loop behavior; this lesson owns the ECMAScript runtime model.

JavaScript Execution Model: Contexts, Realms, Jobs & Agents — Quiz