JavaScript Charts: Formatters

This section explores customization of individual series items and markers based on data they represent.

When it comes to formatters, all series can be divided into two categories:

series with markers, such as line, scatter and area, where each data point is represented by a marker that can be of any shape
series without markers, such as bar and pie, where each data point is represented by a series item with a fixed shape, for example a rectangle or a pie sector

Marker formatter example

If we take a stacked area series where we want the markers of the second subseries to be larger than default size, we could use the following formatter function:

type: 'area',
xKey: 'quarter',
yKeys: ['petrol', 'electric'],
marker: {
    formatter: params => ({
        size: params.yKey === 'electric' ? 12 : params.size
    })
}

Example: Marker Formatter

Series item formatter example

If we have a list of values by country presented via bar series and want the bar for a particular country to stand out, we could use the following formatter function:

type: 'column',
xKey: 'country',
yKeys: ['gdp'],
formatter: params => ({
    fill: params.datum[params.xKey] === 'UK' ? 'red' : params.fill
    // we can also use `params.datum.country`, but the formatter
    // would have to be updated whenever the `xKey` is changed
})

Example: Series Formatter

Please use the API reference to learn more about the marker and series formatters, the inputs they receive and the attributes they allow to customize.

Next Up

Continue to the next section to learn about tooltips.