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Web Workers · 05 TypedArray and Buffer
Series contents · Technology map
Stage: Messages and Execution Contexts · Editable example · Storage ID: web-workers-step-05
Goals and learning outcomes
- Learning outcome: explain the role of View. Input cases: the middle two values of [10,20,30,40].
- Deliverable: a table of sent and received ranges and sums. Explain the rationale for handling Offset, linking it to the code.
Prerequisites
Prepare the experiment results for Copying and Cloning limitations from Unit 4, “Structured Clone”.
Key concepts and explanations
View
A TypedArray is a view interpreting an ArrayBuffer. The view and the underlying storage may cover different ranges.
Offset
subarray points to part of the same storage. Preserve offset and length on the receiving side as well.
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 web-workers-01·02·03 are starting examples. Implement the new assignments in main.js and worker.js in a separate local HTTP project. Preserve CSP and iframe isolation. For SharedArrayBuffer, check COOP and COEP requirements on an external server you control; use the transfer path if they are not met. Measure performance yourself.
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-5.js in a separate practice project, send the full array and a subarray, and print byteOffset, length, and values. Refer to the existing Unit 1·14·28 examples only as starting points.
- Input conditions: the middle two values of [10,20,30,40]. Baseline: Full array. Run under the baseline conditions, then record observations and errors in notes/day-5.md.
- Variable: Range; changed value: Middle subarray. Run again through the same input path. Deliverable to save: a table of sent and received ranges and sums. Hypothesis to check: Only the partial range contributes to the computed sum. Compare it with the actual results, and record whether they agree and why they differ.
Variables to observe
| Variable | Baseline | Change | Expected change / hypothesis |
|---|---|---|---|
| Range | Full array | Middle subarray | Only the partial range contributes to the computed sum. |
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 sent and received ranges and sums. Results are available for both the baseline and changed conditions, allowing comparison of 2 conditions; input values and the execution environment are recorded together.
- The explanation of differences between the two conditions connects both concepts: View and Offset. For unexpected items, at least 1 cause or reason they remain unresolved is recorded.
Self-check
- Which processing stage does View affect in this exercise? Input cases: the middle two values of [10,20,30,40].
- Variable: Range. Hypothesis to check: Only the partial range contributes to the computed sum. Did the actual results agree with the hypothesis? Explain the evidence in terms of Offset.
Official references
Linked example and execution scope
Example source · Runtime environments and limits
An interactive TypedArray and Buffer experiment with cleanup of the resources it uses.
Source code and records are not overwritten automatically. Resetting an existing example also preserves your notes.