Chart annotations in JavaScript Chart control

18 Nov 201823 minutes to read

Chart annotations allow highlighting specific areas of the chart using text, shapes, images, or custom HTML elements. Annotations can be used to emphasize trends, mark thresholds, show custom notes, or display additional information directly inside the chart area.

Annotations are added using the annotations option. Set the content property to reference the element that should be rendered within the chart.

var chartData = [
      { country: "USA", gold: 50, silver: 70, bronze: 45 },
      { country: "China", gold: 40, silver: 60, bronze: 55 },
      { country: "Japan", gold: 70, silver: 60, bronze: 50 },
      { country: "Australia", gold: 60, silver: 56, bronze: 40 },
      { country: "France", gold: 50, silver: 45, bronze: 35 },
      { country: "Germany", gold: 40, silver: 30, bronze: 22 },
      { country: "Italy", gold: 40, silver: 35, bronze: 37 },
      { country: "Sweden", gold: 30, silver: 25, bronze: 27 }
];
var chart = new ej.charts.Chart({
    primaryXAxis: {
        valueType: 'Category',
        // label placement as on ticks
        labelPlacement: 'OnTicks',
        title: 'Countries'
    },
    primaryYAxis: {
        minimum: 0, maximum: 80,
        interval: 20, title: 'Medals'
    },
    annotations:[{
        content: '70 Gold Medals',
        region: 'Series',
        coordinateUnits: 'Point',
        x: 'Japan',
        y: 75
    }],
    series:[{
        dataSource: chartData,
        xName: 'country', yName: 'gold',
        name: 'Gold', type: 'Column'
    }, {
        dataSource: chartData,
        xName: 'country', yName: 'silver',
        name: 'Silver', type: 'Column'
    }, {
        dataSource: chartData,
        xName: 'country', yName: 'bronze',
        name: 'Bronze', type: 'Column'
    }],
    title: 'Olympic Medals'
}, '#element');
<!DOCTYPE html><html lang="en"><head>
    <title>EJ2 Animation</title>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta name="description" content="Typescript UI Controls">
    <meta name="author" content="Syncfusion">
    <link href="index.css" rel="stylesheet">
    
    
<script src="https://cdn.syncfusion.com/ej2/34.1.29/dist/ej2.min.js" type="text/javascript"></script>
</head>

<body>
    
    <div id="container">
        <div id="element"></div>
		   <div id="element1"></div>
    </div>


<script>
var ele = document.getElementById('container');
if(ele) {
  ele.style.visibility = "visible";
}   
      </script>
<script src="index.js" type="text/javascript"></script>
</body></html>

Note: To use the annotation feature, inject ChartAnnotation using Chart.Inject(ChartAnnotation) method.

Region

Annotations can be positioned relative to either the overall Chart area or a specific Series. When placed relative to the chart, the annotation uses the chart’s coordinate system. When placed relative to a series, the annotation aligns with that series’ data points. By default, annotations are placed with respect to the chart.

var chartData = [
      { country: "USA", gold: 50, silver: 70, bronze: 45 },
      { country: "China", gold: 40, silver: 60, bronze: 55 },
      { country: "Japan", gold: 70, silver: 60, bronze: 50 },
      { country: "Australia", gold: 60, silver: 56, bronze: 40 },
      { country: "France", gold: 50, silver: 45, bronze: 35 },
      { country: "Germany", gold: 40, silver: 30, bronze: 22 },
      { country: "Italy", gold: 40, silver: 35, bronze: 37 },
      { country: "Sweden", gold: 30, silver: 25, bronze: 27 }
];
var chart = new ej.charts.Chart({
    primaryXAxis: {
        valueType: 'Category',
        // label placement as on ticks
        labelPlacement: 'OnTicks',
        title: 'Countries'
    },
    primaryYAxis: {
        minimum: 0, maximum: 80,
        interval: 20, title: 'Medals'
    },
    annotations:[{
        content: '70 Gold Medals',
        region: 'Series',
        coordinateUnits: 'Point',
        x: 'Japan',
        y: 75
    }],
    series:[{
        dataSource: chartData,
        xName: 'country', yName: 'gold',
        name: 'Gold', type: 'Column'
    }, {
        dataSource: chartData,
        xName: 'country', yName: 'silver',
        name: 'Silver', type: 'Column'
    }, {
        dataSource: chartData,
        xName: 'country', yName: 'bronze',
        name: 'Bronze', type: 'Column'
    }],
    title: 'Olympic Medals'
}, '#element');
<!DOCTYPE html><html lang="en"><head>
    <title>EJ2 Animation</title>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta name="description" content="Typescript UI Controls">
    <meta name="author" content="Syncfusion">
    <link href="index.css" rel="stylesheet">
    
    
<script src="https://cdn.syncfusion.com/ej2/34.1.29/dist/ej2.min.js" type="text/javascript"></script>
</head>

<body>
    
    <div id="container">
        <div id="element"></div>
		   <div id="element1"></div>
    </div>


<script>
var ele = document.getElementById('container');
if(ele) {
  ele.style.visibility = "visible";
}   
      </script>
<script src="index.js" type="text/javascript"></script>
</body></html>

Co-ordinate units

Use the coordinateUnits property to define how annotation coordinates are interpreted. Choose between:

  • Pixel – The annotation is positioned using fixed pixel values within the chart area.
  • Point – The annotation is positioned based on chart data points (x and y values).
var chartData = [
      { country: "USA", gold: 50, silver: 70, bronze: 45 },
      { country: "China", gold: 40, silver: 60, bronze: 55 },
      { country: "Japan", gold: 70, silver: 60, bronze: 50 },
      { country: "Australia", gold: 60, silver: 56, bronze: 40 },
      { country: "France", gold: 50, silver: 45, bronze: 35 },
      { country: "Germany", gold: 40, silver: 30, bronze: 22 },
      { country: "Italy", gold: 40, silver: 35, bronze: 37 },
      { country: "Sweden", gold: 30, silver: 25, bronze: 27 }
];
var chart = new ej.charts.Chart({
    primaryXAxis: {
        valueType: 'Category',
        // label placement as on ticks
        labelPlacement: 'OnTicks',
        title: 'Countries'
    },
    primaryYAxis: {
        minimum: 0, maximum: 80,
        interval: 20, title: 'Medals'
    },
    annotations:[{
        content: '70 Gold Medals',
        region: 'Series',
        coordinateUnits: 'Point',
        x: 'Japan',
        y: 75
    }],
    series:[{
        dataSource: chartData,
        xName: 'country', yName: 'gold',
        name: 'Gold', type: 'Column'
    }, {
        dataSource: chartData,
        xName: 'country', yName: 'silver',
        name: 'Silver', type: 'Column'
    }, {
        dataSource: chartData,
        xName: 'country', yName: 'bronze',
        name: 'Bronze', type: 'Column'
    }],
    title: 'Olympic Medals'
}, '#element');
<!DOCTYPE html><html lang="en"><head>
    <title>EJ2 Animation</title>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta name="description" content="Typescript UI Controls">
    <meta name="author" content="Syncfusion">
    <link href="index.css" rel="stylesheet">
    
    
<script src="https://cdn.syncfusion.com/ej2/34.1.29/dist/ej2.min.js" type="text/javascript"></script>
</head>

<body>
    
    <div id="container">
        <div id="element"></div>
		   <div id="element1"></div>
    </div>


<script>
var ele = document.getElementById('container');
if(ele) {
  ele.style.visibility = "visible";
}   
      </script>
<script src="index.js" type="text/javascript"></script>
</body></html>

Alignment

Annotation provides verticalAlignment and horizontalAlignment. The verticalAlignment can be customized via Top, Bottom or Middle and the horizontalAlignment can be customized via Near, Far or Center.

var chartData = [
      { country: "USA", gold: 50, silver: 70, bronze: 45 },
      { country: "China", gold: 40, silver: 60, bronze: 55 },
      { country: "Japan", gold: 70, silver: 60, bronze: 50 },
      { country: "Australia", gold: 60, silver: 56, bronze: 40 },
      { country: "France", gold: 50, silver: 45, bronze: 35 },
      { country: "Germany", gold: 40, silver: 30, bronze: 22 },
      { country: "Italy", gold: 40, silver: 35, bronze: 37 },
      { country: "Sweden", gold: 30, silver: 25, bronze: 27 }
];
var chart = new ej.charts.Chart({
    primaryXAxis: {
        valueType: 'Category',
        // label placement as on ticks
        labelPlacement: 'OnTicks',
        title: 'Countries'
    },
    primaryYAxis: {
        minimum: 0, maximum: 80,
        interval: 20, title: 'Medals'
    },
    annotations:[{
        content: '70 Gold Medals',
        region: 'Series',
        coordinateUnits: 'Point',
        x: 'Japan',
        y: 75
    }],
    series:[{
        dataSource: chartData,
        xName: 'country', yName: 'gold',
        name: 'Gold', type: 'Column'
    }, {
        dataSource: chartData,
        xName: 'country', yName: 'silver',
        name: 'Silver', type: 'Column'
    }, {
        dataSource: chartData,
        xName: 'country', yName: 'bronze',
        name: 'Bronze', type: 'Column'
    }],
    title: 'Olympic Medals'
}, '#element');
<!DOCTYPE html><html lang="en"><head>
    <title>EJ2 Animation</title>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta name="description" content="Typescript UI Controls">
    <meta name="author" content="Syncfusion">
    <link href="index.css" rel="stylesheet">
    
    
<script src="https://cdn.syncfusion.com/ej2/34.1.29/dist/ej2.min.js" type="text/javascript"></script>
</head>

<body>
    
    <div id="container">
        <div id="element"></div>
		   <div id="element1"></div>
    </div>


<script>
var ele = document.getElementById('container');
if(ele) {
  ele.style.visibility = "visible";
}   
      </script>
<script src="index.js" type="text/javascript"></script>
</body></html>

Adding y-axis sub title through on annotation

By setting text div in the content option of annotation object you can add sub title to chart y-axis. Specified the coordinate value as pixel and customize x and y location of the text.

var columnData = [{ country: "USA", gold: 50 }, { country: "China", gold: 40 }, { country: "Japan", gold: 70 },
{ country: "Australia", gold: 60 }, { country: "France", gold: 50 }, { country: "Germany", gold: 40 },
{ country: "Italy", gold: 40 }, { country: "Sweden", gold: 30 }];

var chart = new ej.charts.Chart({
    primaryXAxis: {
        valueType: 'Category',
    },
    primaryYAxis: {
        title: '(m2/min)'
    },
    annotations: [{
        content: '<div id="text" style="transform: rotate(-90deg);">Speed Rate</div>',
        x: 6,
        y: 180,
        coordinateUnits: 'Pixel',
        Region: 'Chart'
    }],
    series: [{
        dataSource: columnData,
        xName: 'country', yName: 'gold',
        type: 'Column'
    }],
}, '#element');
<!DOCTYPE html><html lang="en"><head>
    <title>EJ2 Animation</title>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta name="description" content="Typescript UI Controls">
    <meta name="author" content="Syncfusion">
    <link href="index.css" rel="stylesheet">
    
    
<script src="https://cdn.syncfusion.com/ej2/34.1.29/dist/ej2.min.js" type="text/javascript"></script>
</head>

<body>
    
    <div id="container">
        <div id="element"></div>
		   <div id="element1"></div>
    </div>


<script>
var ele = document.getElementById('container');
if(ele) {
  ele.style.visibility = "visible";
}   
      </script>
<script src="index.js" type="text/javascript"></script>
</body></html>

See also