Open code, practice, and notes →
Download source with English comments · for reading
Motion · 23 In-View Animation
Series contents · Technology map
Stage: Validating a Motion System · Editable example · Storage ID: motion-step-23
Goals and learning outcomes
- Learning outcome: Explain the role of InView. Input case: Scrolling into and out of view 3 times.
- Deliverable: The execution count for each repetition. Connect your rationale for handling Once to the code.
Prerequisites
Prepare the results of the UseScroll and Offset exercises from Unit 22, “Scroll-Linked Animation”.
Key concepts and explanations
InView
In-view detection concerns the conditions under which an element is visible. It does not mean the same thing as whether it is rendered.
Once
once limits execution to the first entrance. Match it to the intent of content shown repeatedly.
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-23.tsx of a separate exercise project, configure whileInView and viewport.once. Use the existing Unit 1·14·28 examples only as starting points.
- Input condition: Scrolling into and out of view 3 times. Baseline: false. Run under the baseline condition, then record observations and errors in notes/day-23.md.
- Variable to change: once; new value: true. Run again with the same input path. Deliverable to save: The execution count for each repetition. Hypothesis to test: Repeated motion is skipped from the second entrance onward. 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 |
|---|---|---|---|
| once | false | true | Repeated motion is skipped from the second entrance onward. |
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: The execution count for each repetition. 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: InView and Once. For unexpected items, give at least 1 cause or reason they remain unresolved.
Self-check
- Which processing stage does InView affect in this exercise? Input case: Scrolling into and out of view 3 times.
- Variable to change: once. Hypothesis to test: Repeated motion is skipped from the second entrance onward. Did the actual results agree with the hypothesis? Explain your evidence in terms of Once.
Official references
Linked example and execution scope
Example source · Runtime environments and limits
Interactive In-View Animation 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: Scroll-Linked Animation · Next: UseAnimate Cleanup