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TypeScript · 27 Plugin Ownership and Cleanup Contracts

Series contents · Technology map

Stage: Module Contracts and Plugins · Editable example · Storage ID: typescript-step-27

Goals and learning outcomes

• The event handler runs 0 times after cleanup.
• The remounted button handles a click 1 time.

Prerequisites

Work and experiment records from Unit 26, “Cases That Verify Compilation Failures”

Key concepts and explanations

Common Interfaces

Define implementation boundaries with mount and dispose contracts. Pass only the DOM and configuration needed in the context.

Lifecycle

Event leaks can occur even with matching types. Check repeated mounting and duplicate disposal at runtime.

Practice setup

First check the execution scope guidance on the example screen. The following environment is for extending the assignment in a separate project. Implement it yourself in a separate local project and check it with browser developer tools and tsc --noEmit. Record the installed tsc version in a separate TypeScript project. Enable strict in tsconfig.json and check with tsc --noEmit, then open the runtime exercise using compiled output or a local development server. Do not assume the browser executes TS type annotations directly.

The linked example is a starting point. It does not implement every task below. Complete work beyond its supported scope in a separate project.

Practice tasks

1. In plugin.ts, prepare conditions for 5 mounts and 2 consecutive dispose calls.
2. Define Plugin and Context, and write a resource cleanup list in one DOM implementation.
3. Run with 5 mounts and 2 consecutive dispose calls. Results to check: The event handler runs 0 times after cleanup. The remounted button handles a click 1 time. Record expected and actual results separately.

Variables to observe

Predictions in this table are not measured results. Change one condition at a time and record why the actual result differs.

Completion criteria

• The event handler runs 0 times after cleanup.
• The remounted button handles a click 1 time.

Self-check

1. Does an interface enforce resource cleanup?
2. May a plugin delete resources it does not own?

Official references

• TypeScript Handbook

Linked example and execution scope

Example source · Runtime environments and limits

The preview is a JavaScript runtime boundary experiment. It does not run TypeScript diagnostics. Check lesson.ts locally with tsc --strict --noEmit --lib ES2023,DOM.

• example.js
• lesson.ts

Source code and records are not overwritten automatically. Resetting an existing example also preserves your notes.

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Previous: Cases That Verify Compilation Failures · Next: Plugin Contracts

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