4.x迁移指南

Chart.js 4.0 introduces a number of breaking changes. We tried keeping the amount of breaking changes to a minimum. For some features and bug fixes it was necessary to break backwards compatibility, but we aimed to do so only when worth the benefit.

## End user migration
### Charts
- Charts don't override the default tooltip callbacks, so all chart types have the same-looking tooltips.
- Default scale override has been removed if the configured scale starts with `x/y`. Defining `xAxes` in your config will now create a second scale instead of overriding the default x axis.

### Options
A number of changes were made to the configuration options passed to the Chart constructor. Those changes are documented below.

#### Specific changes
- The radialLinear grid indexable and scriptable options don't decrease the index of the specified grid line anymore.
- The destroy plugin hook has been removed and replaced with afterDestroy.
- Ticks callback on time scale now receives timestamp instead of a formatted label.
- scales[id].grid.drawBorder has been renamed to scales[id].border.display.
- scales[id].grid.borderWidth has been renamed to scales[id].border.width.
- scales[id].grid.borderColor has been renamed to scales[id].border.color.
- scales[id].grid.borderDash has been renamed to scales[id].border.dash.
- scales[id].grid.borderDashOffset has been renamed to scales[id].border.dashOffset.
- The z index for the border of a scale is now configurable instead of being 1 higher as the grid z index.
- Linear scales now add and subtracts 5% of the max value to the range if the min and max are the same instead of 1.
- If the tooltip callback returns undefined, then the default callback will be used.
- maintainAspectRatio respects container height.
- Time and timeseries scales use ticks.stepSize instead of time.stepSize, which has been removed.
- maxTickslimit wont be used for the ticks in autoSkip if the determined max ticks is less then the maxTicksLimit.
- dist/chart.js has been removed.
- dist/chart.min.js has been renamed to dist/chart.umd.js.
- dist/chart.esm.js has been renamed to dist/chart.js.

#### Type changes
The order of the ChartMeta parameters have been changed from `<Element, DatasetElement, Type>` to `<Type, Element, DatasetElement>.`

### General
- Chart.js becomes an ESM-only package (the UMD bundle is still available). To use Chart.js, your project should also be an ES module. Make sure to have this in your package.json:
```javascript
{
  "type": "module"
}
```

If you are experiencing problems with Jest , follow its documentation to enable the ESM support. Or, we can recommend you migrating to Vitest . Vitest has the ESM support out of the box and almost the same API as Jest . See an example of migration .
- Removed fallback to fontColor for the legend text and strikethrough color.
- Removed config._chart fallback for this.chart in the filler plugin.
- Removed this._chart in the filler plugin.