Open code, practice, and notes →
Download source with English comments · for reading
Motion · 25 Reduced Motion Policy
Series contents · Technology map
Stage: Validating a Motion System · Editable example · Storage ID: motion-step-25
Goals and learning outcomes
- Learning outcome: Explain the role of Detecting preferences. Input case: Selection, sorting, and deletion.
- Deliverable: A table of final data and content in default and reduced modes. Connect your rationale for handling Preserving content to the code.
Prerequisites
Prepare the results of the Scope and Asynchronous order exercises from Unit 24, “UseAnimate Cleanup”.
Key concepts and explanations
Detecting preferences
useReducedMotion reads the user's preference. MotionConfig also supports a reducedMotion policy.
Preserving content
Selection and order must remain even when movement is reduced. Adjust opacity changes too if they make content unreadable.
Practice setup
First check the execution scope guidance on the example screen. The following describes the environment needed to extend the assignment in a separate project. The existing motion-01·02·03 examples are limited examples based on Motion JS animate. For React layout, AnimatePresence, and hooks exercises, install motion in a separate local React project and import from motion/react. Do not assume JSX runs directly in the editor; preserve CSP and isolation.
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
- In src/day-25.tsx of a separate exercise project, skip the x transition based on useReducedMotion and apply the same target state. Use the existing Unit 1·14·28 examples only as starting points.
- Input condition: Selection, sorting, and deletion. Baseline: Default. Run under the baseline condition, then record observations and errors in notes/day-25.md.
- Variable to change: Preference; new value: reduce. Run again with the same input path. Deliverable to save: A table of final data and content in default and reduced modes. Hypothesis to test: Functional results and readable content stay the same. Compare it with the actual results and record whether they agree and the causes of any differences.
Variables to observe
| Variable | Baseline | Change | Expected change / hypothesis |
|---|---|---|---|
| Preference | Default | reduce | Functional results and readable content stay the same. |
Predictions in this table are not measured results. Change one condition at a time and record why the actual result differs.
Completion criteria
- Required deliverable: A table of final data and content in default and reduced modes. You have results for both the baseline and changed conditions, allowing a comparison of 2 conditions, and have recorded the input values and execution environment.
- Your explanation of the differences between the two conditions connects both concepts: Detecting preferences and Preserving content. For unexpected items, give at least 1 cause or reason they remain unresolved.
Self-check
- Which processing stage does Detecting preferences affect in this exercise? Input case: Selection, sorting, and deletion.
- Variable to change: Preference. Hypothesis to test: Functional results and readable content stay the same. Did the actual results agree with the hypothesis? Explain your evidence in terms of Preserving content.
Official references
Linked example and execution scope
Example source · Runtime environments and limits
Interactive Reduced Motion Policy experiment with cleanup of the resources used.
Source code and records are not overwritten automatically. Resetting an existing example also preserves your notes.
Next learning
Previous: UseAnimate Cleanup · Next: Observing Renders and Performance