feat(chartjs): add Bump Chart template#60
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Port the Bump template to the Chart.js backend, mirroring the ECharts implementation (ecBumpChartDef): line-with-points per series over a shared x axis, with the rank axis reversed so rank 1 sits on top. Chart.js reverses a linear scale in place (reverse: true), so unlike the ECharts category-index workaround the series keep their real rank values and the config stays pure JSON with no tooltip formatter. Rank detection mirrors the shared rule (Rank/Score/Level semantic on y and not on x); non-rank inputs fall back to a plain value axis with the semantic zero decision, like the Line template. Discrete/temporal/ linear x handling and the continuous-extent pinning follow line.ts. - register in cjsTemplateDefs (Line & Area group, same position as ECharts) - tests: 6 cases (registry, datasets shape, reversed rank axis pinned to [1, maxRank], non-rank fallback, JSON round-trip purity, 3-backend parity) - docs: regenerate reference-chartjs.md; add Bump to the SKILL.md Chart.js coverage list (+ synced bundled asset) Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Chenglong-MS
approved these changes
Jul 20, 2026
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What
The Vega-Lite and ECharts backends ship a Bump Chart template; Chart.js doesn't —
assembleChartjsthrows onBump Chart. This PR ports the template, mirroring the ECharts implementation.Implementation
Line datasets per series over the shared category (time) axis, with y carrying true rank values and
reverse: trueon the scale — Chart.js supports reversed linear axes natively. That removes the category-index workaround the ECharts template needs. Rank-semantics detection (Rank / Score / Level) and the fallback to a plain value axis for non-rank measures mirror the ECharts template. Registered in theLine & Areagroup, same position as ECharts. The compiled config is plain JSON (no callback functions).One cross-backend observation from verification: on the same input, VL puts rank 3 on top while ECharts puts rank 1 on top. The VL template's own comment intends rank 1 on top ("reverse Y so rank 1 is at top"), so this may be a double reversal — Rank semantics already reverse the axis before the template sets
reverseagain. This PR follows ECharts, which matches the documented Rank behavior; happy to file the VL side separately.Verification
tests/bump-chartjs.test.ts— 6 cases: registry, one dataset per series, reversed rank axis pinned to[1, maxRank], non-rank fallback to a plain value axis, JSON round-trip, 3-backend paritydocs/reference-chartjs.mdregenerated vianpm run gen:referenceserver.test.ts)Side-by-side render vs Vega-Lite and ECharts (same input):
Note: #59 and this PR both append one line to
templates/index.tsand the SKILL.md coverage list; whichever lands second needs a trivial rebase + asset re-sync.🤖 Generated with Claude Code