# Options
# Option resolution
Options are resolved from top to bottom, using a context dependent route.
# Chart level options
- options
- overrides[
config.type
] - defaults
# Dataset level options
dataset.type
defaults to config.type
, if not specified.
- dataset
- options.datasets[
dataset.type
] - options
- overrides[
config.type
].datasets[dataset.type
] - defaults.datasets[
dataset.type
] - defaults
# Dataset animation options
- dataset.animation
- options.datasets[
dataset.type
].animation - options.animation
- overrides[
config.type
].datasets[dataset.type
].animation - defaults.datasets[
dataset.type
].animation - defaults.animation
# Dataset element level options
Each scope is looked up with elementType
prefix in the option name first, then without the prefix. For example, radius
for point
element is looked up using pointRadius
and if that does not hit, then radius
.
- dataset
- options.datasets[
dataset.type
] - options.datasets[
dataset.type
].elements[elementType
] - options.elements[
elementType
] - options
- overrides[
config.type
].datasets[dataset.type
] - overrides[
config.type
].datasets[dataset.type
].elements[elementType
] - defaults.datasets[
dataset.type
] - defaults.datasets[
dataset.type
].elements[elementType
] - defaults.elements[
elementType
] - defaults
# Scale options
- options.scales
- overrides[
config.type
].scales - defaults.scales
- defaults.scale
# Plugin options
A plugin can provide additionalOptionScopes
array of paths to additionally look for its options in. For root scope, use empty string: ''
. Most core plugins also take options from root scope.
- options.plugins[
plugin.id
] - (options.[
...plugin.additionalOptionScopes
]) - overrides[
config.type
].plugins[plugin.id
] - defaults.plugins[
plugin.id
] - (defaults.[
...plugin.additionalOptionScopes
])
# Scriptable Options
Scriptable options also accept a function which is called for each of the underlying data values and that takes the unique argument context
representing contextual information (see option context).
A resolver is passed as second parameter, that can be used to access other options in the same context.
Note
The context
argument should be validated in the scriptable function, because the function can be invoked in different contexts. The type
field is a good candidate for this validation.
Example:
color: function(context) {
const index = context.dataIndex;
const value = context.dataset.data[index];
return value < 0 ? 'red' : // draw negative values in red
index % 2 ? 'blue' : // else, alternate values in blue and green
'green';
},
borderColor: function(context, options) {
const color = options.color; // resolve the value of another scriptable option: 'red', 'blue' or 'green'
return Chart.helpers.color(color).lighten(0.2);
}
# Indexable Options
Indexable options also accept an array in which each item corresponds to the element at the same index. Note that if there are less items than data, the items are looped over. In many cases, using a function is more appropriate if supported.
Example:
color: [
'red', // color for data at index 0
'blue', // color for data at index 1
'green', // color for data at index 2
'black', // color for data at index 3
//...
]
# Option Context
The option context is used to give contextual information when resolving options and currently only applies to scriptable options. The object is preserved, so it can be used to store and pass information between calls.
There are multiple levels of context objects:
chart
dataset
data
scale
tick
pointLabel
(only used in the radial linear scale)
tooltip
Each level inherits its parent(s) and any contextual information stored in the parent is available through the child.
The context object contains the following properties:
# chart
chart
: the associated charttype
:'chart'
# dataset
In addition to chart
active
: true if element is active (hovered)dataset
: dataset at indexdatasetIndex
datasetIndex
: index of the current datasetindex
: same asdatasetIndex
mode
: the update modetype
:'dataset'
# data
In addition to dataset
active
: true if element is active (hovered)dataIndex
: index of the current dataparsed
: the parsed data values for the givendataIndex
anddatasetIndex
raw
: the raw data values for the givendataIndex
anddatasetIndex
element
: the element (point, arc, bar, etc.) for this dataindex
: same asdataIndex
type
:'data'
# scale
In addition to chart
scale
: the associated scaletype
:'scale'
# tick
In addition to scale
tick
: the associated tick objectindex
: tick indextype
:'tick'
# tooltip
In addition to chart
tooltip
: the tooltip objecttooltipItems
: the items the tooltip is displaying