This is a fork of chartjs-plugin-crosshair which supports displaying interpolated values for line charts

Chart.js plugin to draw vertical crosshair, zoom, interpolate values and sync chart interactions.

Requires Chart.js 4.4.0 or later.

Documentation

• Installation
• Options
• Samples

Example

new Chart(ctx, {
  // ... data ...
  options: {
    // ... other options ...
    plugins: {
      tooltip: {
        mode: 'interpolate',
        intersect: false,
        callbacks: {
          title: ([i]) => {
            let x = i?.element?.x
            x = x || x === 0 ? x.toFixed(2) : ""
  
            return x
          },
          label: i => {
            let label = i?.dataset?.label || ""
            if (label) label = `${label}: `
  
            let val = i?.element?.y
            val = val || val === 0 ? val.toFixed(2) : ""
  
            return `${label}${val}`
          },
        },
      },
      crosshair: {
        line: {
          color: '#F66',  // crosshair line color
          width: 1        // crosshair line width
        },
        sync: {
          enabled: true,            // enable trace line syncing with other charts
          group: 1,                 // chart group
          suppressTooltips: false   // suppress tooltips when showing a synced tracer
        },
        zoom: {
          enabled: true,                                      // enable zooming
          zoomboxBackgroundColor: 'rgba(66,133,244,0.2)',     // background color of zoom box 
          zoomboxBorderColor: '#48F',                         // border color of zoom box
          zoomButtonText: 'Reset Zoom',                       // reset zoom button text
          zoomButtonClass: 'reset-zoom',                      // reset zoom button class
        },
        callbacks: {
          beforeZoom: () => function(start, end) {                  // called before zoom, return false to prevent zoom
            return true;
          },
          afterZoom: () => function(start, end) {                   // called after zoom
          }
        }
      }
    }
  }
});

Development

You first need to install node dependencies (requires Node.js):

> npm install

The following commands will then be available from the repository root:

> gulp build            // build dist files
> gulp build --watch    // build and watch for changes
> gulp lint             // perform code linting
> gulp docs             // generate GitBook documentation (`dist/docs`)
> gulp samples          // prepare samples for release (`dist/samples`)
> gulp package          // create an archive with dist files and samples
> gulp netlify          // prepare Netlify artifacts (`dist/www`)

License

chartjs-plugin-crosshair is available under the MIT license.