Chart.js/docs/general/data-structures.md

Data structures

The data property of a dataset can be passed in various formats. By default, that data is parsed using the associated chart type and scales.

Primitive[]

data: [20, 10],
labels: ['a', 'b']

When the data is an array of numbers, values from labels array at the same index are used for the index axis (x for vertical, y for horizontal charts).

Object[]

data: [{x: 10, y: 20}, {x: 15, y: 10}]

data: [{x:'2016-12-25', y:20}, {x:'2016-12-26', y:10}]

data: [{x:'Sales', y:20}, {x:'Revenue', y:10}]

This is also the internal format used for parsed data. Property names are matched to scale-id. In this mode, parsing can be disabled by specifying parsing: false at chart options or dataset. If parsing is disabled, data must be in the formats the associated chart type and scales use internally.

Object

data: {
    January: 10,
    February: 20
}

In this mode, property name is used for index scale and value for value scale. For vertical charts, index scale is x and value scale is y.