Added
- CSP safety: refactored to avoid usage of function constructors from `basic`, `cartesian`, `finance`, `geo`, and `mapbox`
partial bundles and added tests to ensure that they will not again do so in the future [[5359](https://github.com/plotly/plotly.js/pull/5359), [#5383](https://github.com/plotly/plotly.js/pull/5383), [#5387](https://github.com/plotly/plotly.js/pull/5387)],
with thanks to [Equinor](https://www.equinor.com) for sponsoring the related development!
- Add `strict` partial bundle [[5413](https://github.com/plotly/plotly.js/pull/5413), [#5444](https://github.com/plotly/plotly.js/pull/5444)], which includes
the maximal subset of the library which does not rely on function constructors
- Add `custom-bundle` script to facilitate generation of custom bundles [[5527](https://github.com/plotly/plotly.js/pull/5527), [#5508](https://github.com/plotly/plotly.js/pull/5508), [#5605](https://github.com/plotly/plotly.js/pull/5605), [#5712](https://github.com/plotly/plotly.js/pull/5712)]
- Add mock validation utility [[5653](https://github.com/plotly/plotly.js/pull/5653)]
- Implement "fast" `zsmooth` option for `image` trace [[5354](https://github.com/plotly/plotly.js/pull/5354), [#5386](https://github.com/plotly/plotly.js/pull/5386)],
with thanks to almarklein for the contribution!
- Implement various `marker.pattern` options in `histogram`, `bar` and `barpolar` traces [[5520](https://github.com/plotly/plotly.js/pull/5520), [#5537](https://github.com/plotly/plotly.js/pull/5537)]
with thanks to s417-lama for the contribution!
- Implement `ticklabeloverflow` options on cartesian axes and colorbars to drop tick labels going outside div or domain [[5584](https://github.com/plotly/plotly.js/pull/5584)]
- Implement `(x|y|z)hoverformat`, `(u|v|w)hoverformat` and `valueformat` to cartesian and gl3d traces [[5563](https://github.com/plotly/plotly.js/pull/5563)]
- Implement "(x|y)other" `hovertemplate` options to format differing positions in compare and unified modes [[5690](https://github.com/plotly/plotly.js/pull/5690)]
- Add layout and template attributes to facilitate enabling and disabling predefined modebar buttons e.g. shape drawing and "v1hovermode" via `modebar.add` and `modebar.remove` [[5660](https://github.com/plotly/plotly.js/pull/5660)]
Removed
- Drop support for old browsers IE9 and IE10 [[5376](https://github.com/plotly/plotly.js/pull/5376), [#5380](https://github.com/plotly/plotly.js/pull/5380), [#5460](https://github.com/plotly/plotly.js/pull/5460), [#5491](https://github.com/plotly/plotly.js/pull/5491)]
- Stop exporting v3 of d3 under `Plotly.d3` [[5400](https://github.com/plotly/plotly.js/pull/5400), [#5406](https://github.com/plotly/plotly.js/pull/5406)]
- Stop attaching `_has*` plot types to `fullLayout` [[5409](https://github.com/plotly/plotly.js/pull/5409)]
- Stop injecting MathJax config by default [[5514](https://github.com/plotly/plotly.js/pull/5514)]
- Remove `sane-topojson` and MathJax v2.3 files from dist folder and change supported MathJax version to v2.7.5 [[5487](https://github.com/plotly/plotly.js/pull/5487), [#5492](https://github.com/plotly/plotly.js/pull/5492), [#5494](https://github.com/plotly/plotly.js/pull/5494)]
- Reduce the number of exported methods from `Plotly.Fx` and `Plotly.Plots` in the API [[5420](https://github.com/plotly/plotly.js/pull/5420)]
- Drop `Plotly.plot` from the API [[5412](https://github.com/plotly/plotly.js/pull/5412), [#5370](https://github.com/plotly/plotly.js/pull/5370), [#5393](https://github.com/plotly/plotly.js/pull/5393)]
- Drop `Plotly.Queue` from the API [[5423](https://github.com/plotly/plotly.js/pull/5423)]
- Drop non-object `role` keys from attribute definition [[5425](https://github.com/plotly/plotly.js/pull/5425), [#5432](https://github.com/plotly/plotly.js/pull/5432)]
- Drop deprecated `contourgl` and `area` traces as well as deprecated legacy
pre-`scatterpolar` polar-related attributes `bar.t`, `bar.r`,
`scatter.t`, `scatter.r`, `layout.radialaxis`, `layout.angularaxis` and
`gd.framework` [[5399](https://github.com/plotly/plotly.js/pull/5399), [#5408](https://github.com/plotly/plotly.js/pull/5408), [#5409](https://github.com/plotly/plotly.js/pull/5409), [#5398](https://github.com/plotly/plotly.js/pull/5398), [#5438](https://github.com/plotly/plotly.js/pull/5438)]
- Stop overwriting the "latest" bundles on CDN, please specify the version [[5462](https://github.com/plotly/plotly.js/pull/5462), [#5697](https://github.com/plotly/plotly.js/pull/#5697)]
Deprecated
- Deprecate `heatmapgl` and `pointcloud` trace types for later removal [[5447](https://github.com/plotly/plotly.js/pull/5447)]
- Deprecate `transform` attributes [[5657](https://github.com/plotly/plotly.js/pull/5657)]
Changed
- No longer show "Aa" text in legends unless there is only text in the legend item [[5682](https://github.com/plotly/plotly.js/pull/5682)]
- New defaults for `legend.title.font` and `colorbar.title.font` to depend on `legend.font` and `colorbar.tickfont` and increase their sizes [[5611](https://github.com/plotly/plotly.js/pull/5611)]
- New defaults for spikes by setting `spikedistance` to "-1" and `axis.spikesnap` to "hovered data" [[5648](https://github.com/plotly/plotly.js/pull/5648)]
- Default `hovermode` to "closest" [[5647](https://github.com/plotly/plotly.js/pull/5647)]
- Default `textposition` to "auto" in `bar`, `histogram` and `waterfall` traces [[5638](https://github.com/plotly/plotly.js/pull/5638)]
- Hide hover and spike modebar buttons by default while `layout.modebar.add` or `config.modeBarButtonsToAdd` could be used to bring them back in [[5654](https://github.com/plotly/plotly.js/pull/5654), [#5658](https://github.com/plotly/plotly.js/pull/5658)]
- Switch to `native-promise-only` module to handle es6 promises [[5358](https://github.com/plotly/plotly.js/pull/5358)]
- Switch to `probe-image-size` module to get width and height of images [[5388](https://github.com/plotly/plotly.js/pull/5388), [#5635](https://github.com/plotly/plotly.js/pull/#5635)]
- Relax test for plain objects to enable validation in node.js and multiple window contexts [[5411](https://github.com/plotly/plotly.js/pull/5411), [#5498](https://github.com/plotly/plotly.js/pull/5498)]
- Display latitudes before longitudes in mapbox and geo hoverlabels to comply with ISO 6709 (Standard representation of geographic point location by coordinates) [[5485](https://github.com/plotly/plotly.js/pull/5485), [#5676](https://github.com/plotly/plotly.js/pull/5676)]
- Adjust text shadow color in respect to `paper_bgcolor` for better dark mode display of
`sankey`, `parcoords` and `parcats` traces [[5506](https://github.com/plotly/plotly.js/pull/5506)]
- Improve `sankey` text namely support pseudo-html, fix `textfont.color` and avoid clipping [[5531](https://github.com/plotly/plotly.js/pull/5531)]
- Make selection event data of `scattergl` on par with `scatter` traces [[5534](https://github.com/plotly/plotly.js/pull/5534)]
- Fire `plotly_unhover` event when dragging [[5407](https://github.com/plotly/plotly.js/pull/5407)],
with thanks to rreusser for the contribution!
- Include transforms and calendars in partial bundles [[5379](https://github.com/plotly/plotly.js/pull/5379), [#5422](https://github.com/plotly/plotly.js/pull/5422)]
- Require unminified `mapbox-gl` dependency for unminified bundles and
revisit compression options for minified bundles [[5449](https://github.com/plotly/plotly.js/pull/5449)]
- Remove header comments from the source files and only add headers to the top of
dist files at build time [[5436](https://github.com/plotly/plotly.js/pull/5436), [#5446](https://github.com/plotly/plotly.js/pull/5446)]
- Guard against unexpected characters at build time [[5424](https://github.com/plotly/plotly.js/pull/5424)]
- Minimize indentation in plot-schema [[5663](https://github.com/plotly/plotly.js/pull/5663)]
- More maintenance work listed under [the 60th milestone](https://github.com/plotly/plotly.js/milestone/60?closed=1)!
Fixed
- Fix "toself" `fill` for `scattergl` traces to handle multiple polygons [[5355](https://github.com/plotly/plotly.js/pull/5355)],
with thanks to ruijin for the contribution!
- Fix element targeting on hover in shadow DOM [[5256](https://github.com/plotly/plotly.js/pull/5256)],
with thanks to dbluhm for the contribution!
- Fix hover interaction on geo subplots in Firefox [[5607](https://github.com/plotly/plotly.js/pull/5607)],
with thanks to LucaVazz for the contribution!
- Improve `scattergl` performance when using typed arrays [[5632](https://github.com/plotly/plotly.js/pull/5632)],
with thanks to Seranicio for the contribution!
- Fix native ES6 import [[5708](https://github.com/plotly/plotly.js/pull/5708)],
with thanks to oldrich-svec suggestion!
- Hide gridlines and ticks overlapping "inside" ticklabels [[5550](https://github.com/plotly/plotly.js/pull/5550), [#5586](https://github.com/plotly/plotly.js/pull/5586), [#5589](https://github.com/plotly/plotly.js/pull/5589), [#5610](https://github.com/plotly/plotly.js/pull/5610), [#5684](https://github.com/plotly/plotly.js/pull/5684)]
- Improve hover in compare and unified modes [[5543](https://github.com/plotly/plotly.js/pull/5543), [#5618](https://github.com/plotly/plotly.js/pull/5618), [#5662](https://github.com/plotly/plotly.js/pull/5662), [#5664](https://github.com/plotly/plotly.js/pull/5664), [#5668](https://github.com/plotly/plotly.js/pull/5668), [#5683](https://github.com/plotly/plotly.js/pull/5683)]
- Fix spike on `bar`-like traces [[5542](https://github.com/plotly/plotly.js/pull/5542)]
- Fix `bar` inside text font color default when using colorscale [[5666](https://github.com/plotly/plotly.js/pull/5666)]
- Fix `texttemplate` on log axes [[5622](https://github.com/plotly/plotly.js/pull/5622)]
- Fix displaying zero `threshold` for `indicator` trace [[5430](https://github.com/plotly/plotly.js/pull/5430)]
- Fix axis constraints for `heatmapgl` [[5476](https://github.com/plotly/plotly.js/pull/5476)]
- Fix setTimeout functions to return in the case of undefined layouts [[5482](https://github.com/plotly/plotly.js/pull/5482)]
- Fix misinterpreted clip-path by some programs after export [[5686](https://github.com/plotly/plotly.js/pull/5686)]
- Avoid redundant number casting in `Lib.ensureNumber` function [[5637](https://github.com/plotly/plotly.js/pull/5637)]
- Avoid duplicate keys in object literals within plotly builds [[5458](https://github.com/plotly/plotly.js/pull/5458)]
- Revise attributions of Carto, Stamen and Open Street Map styles [[5696](https://github.com/plotly/plotly.js/pull/5696)]
- Improve attribute compression and avoid redundant copyright comments in non-minified
bundles [[5426](https://github.com/plotly/plotly.js/pull/5426), [#5429](https://github.com/plotly/plotly.js/pull/5429), [#5439](https://github.com/plotly/plotly.js/pull/5439)]
- Provide links to all pull requests in the changelog [[5469](https://github.com/plotly/plotly.js/pull/5469)]
- Provide documention for creating custom bundles and improve readme files [[5702](https://github.com/plotly/plotly.js/pull/#5702), [5703](https://github.com/plotly/plotly.js/pull/#5703), [5704](https://github.com/plotly/plotly.js/pull/#5704), [5705](https://github.com/plotly/plotly.js/pull/#5705), [5713](https://github.com/plotly/plotly.js/pull/#5713)]
- Provide a link to plotly.js dependencies when publishing various plotly.js-dist packages to npm [[5711](https://github.com/plotly/plotly.js/pull/5711)]
- Adjust npm publish script to use relevant tag e.g. "rc" when publishing various plotly.js-dist packages [[5467](https://github.com/plotly/plotly.js/pull/5467)]
- Place CDN publish script inside plotly.js repository [[5468](https://github.com/plotly/plotly.js/pull/5468), [#5470](https://github.com/plotly/plotly.js/pull/5470)]
- Fix syntax test on the dist files [[5471](https://github.com/plotly/plotly.js/pull/5471)]