Chart.js get the nearest point when clicked on canvas

Question

is there a way to get the nearest point when clicked anywhere on canvas? Maybe somehow harvest the core 'nearest' method? Thanks

Answer 1

I think you will find getElementsAtXAxis very helpful.

Basically, getElementsAtXAxis has a very similar behaviour to getElementsAtEvent although when the click event doesn't intersect a point of the chart, it will return the nearest ChartElement.

The only downside is that it will return all the ChartElement on the nearest x-axis index.

So, if you use multiple datasets, this might not be the best choice for you.

Code example:

canvas.onclick = function(e) {
    const elts = chart.getElementsAtXAxis(simulatedEvent);
    if (elts && elts.length) {
        // Do something with elts[0]
    }
};

If anyone is looking for the related piece of code, it's in core.controller.js:

getElementAtEvent: function(e) {
    return Interaction.modes.nearest(this, e, {intersect: true});
},

getElementsAtEvent: function(e) {
    return Interaction.modes.index(this, e, {intersect: true});
},

getElementsAtXAxis: function(e) {
    return Interaction.modes.index(this, e, {intersect: false});
},