tooltip callback cannot recognize metadata (TS 2339) - chart.js

Question

I have the following toy data:
export const playData = {
datasets: [
{
label: 'Dataset 1',
showLine: true,
data: [{ x: 1, y: 10, name: 'John' }, { x: 2, y: 5, name: 'Linda' }, { x: 3, y: 7, name: 'Erin' }, { x: 4, y: 4, name: 'Chloe' }, { x: 5, y: 8, name: 'Paul' }],
borderColor: 'rgb(255, 99, 132)',
backgroundColor: 'rgba(255, 99, 132, 0.5)',
},
};
I am then trying to make a custom tooltip showing this data, which works as expected:
export function Chart(props: { chartData: ChartData }) {
return <Scatter
data={props.chartData}
options={{
responsive: true,
scales: {
x: {
title: {
display: true,
text: 'Age (years)'
},
},
y: {
title: {
display: true,
text: 'Change in Height (inches)'
}
}
},
plugins: {
legend: {
position: 'top' as const,
},
tooltip: {
callbacks: {
label: (context) => {
return [context.raw.name, `age: ${context.parsed.x} years`, `height change: ${context.parsed.y} in`]
}
}
}
},
}}
/>;
}
But TS underlines the final context.raw.name and says
Property 'name' does not exist on type 'unknown'.ts(2339)
How can I fix this?

Answer 1

You can create your own custom interface by extending the one that is already being used and add the custom option you added to your dataset:
import { Chart, TooltipItem } from 'chart.js';
interface CustomTooltipItem extends TooltipItem<'scatter'> {
raw: {
x: number,
y: number,
name: string,
}
}
const ctx = document.getElementById("myChart") as HTMLCanvasElement;
const myChart = new Chart(ctx, {
type: 'scatter',
data: {
datasets: [{
label: '# of Votes',
data: [{ x: 1, y: 10, name: 'John' }, { x: 2, y: 5, name: 'Linda' }, { x: 3, y: 7, name: 'Erin' }, { x: 4, y: 4, name: 'Chloe' }, { x: 5, y: 8, name: 'Paul' }],
}]
},
options: {
plugins: {
tooltip: {
callbacks: {
label: (context: CustomTooltipItem) => {
return [context.raw.name, `age: ${context.parsed.x} years`, `height change: ${context.parsed.y} in`]
}
}
}
}
}
});
https://www.typescriptlang.org/play?#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