{
    annotation: {
        annotations: [{
            type: 'line',
            mode: 'horizontal',
            scaleID: 'y-axis-0',
            value: '25',
            borderColor: 'red',
            borderWidth: 2
        }],
        // Defines when the annotations are drawn.
        // This allows positioning of the annotation relative to the other
        // elements of the graph.
        // Should be one of: afterDraw, afterDatasetsDraw, beforeDatasetsDraw
        // See http://www.chartjs.org/docs/#advanced-usage-creating-plugins
        drawTime: "afterDraw" // (default)
    }
}

{
    type: 'line',
    // set to 'vertical' to draw a vertical line
    mode: 'horizontal',

    // ID of the scale to bind onto
    scaleID: 'y-axis-0',

    // Data value to draw the line at
    value: 25,

    // Optional value at which the line draw should end
    endValue: 26,

    // Line color
    borderColor: 'red',

    // Line width
    borderWidth: 2,

    // Line dash
    // https://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D/setLineDash
    borderDash: [2, 2],

    // Line Dash Offset
    // https://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D/lineDashOffset
    borderDashOffset: 5
}

{
    type: 'box',

    // ID of the X scale to bind onto
    xScaleID: 'x-axis-0',

    // ID of the Y scale to bind onto
    yScaleID: 'y-axis-0',

    // Left edge of the box. in units along the x axis
    xMin: 25,

    // Right edge of the box
    xMax: 40,

    // Top edge of the box in units along the y axis
    yMax: 20,

    // Bottom edge of the box
    yMin:  15,

    // Stroke color
    borderColor: 'red',

    // Stroke width
    borderWidth: 2,

    // Fill color
    backgroundColor: 'green'
}