Labels in EJ2 JavaScript Diagram control

30 Jun 202415 minutes to read

Annotation is a block of text that can be displayed over a node or connector. Annotation is used to textually represent an object with a string that can be edited at runtime. Multiple annotations can be added to a node/connector.

Create annotation

An annotation can be added to a node/connector by defining the annotation object and adding that to the annotation collection of the node/connector. The content property of annotation defines the text to be displayed. The following code illustrates how to create a annotation.

index.js
index.html
var node = {
    id: 'node1',
    // Position of the node
    offsetX: 100,
    offsetY: 100,
    // Size of the node
    width: 100,
    height: 100,
    style: {
      fill: '#6BA5D7',
      strokeColor: 'white',
    },
    // Sets the Annotation for the Node
    annotations: [
      {
        // Sets the text to be displayed
        content: 'Annotation',
      },
    ],
  };
  
  var connector = {
    sourcePoint: {
      x: 300,
      y: 100,
    },
    targetPoint: {
      x: 400,
      y: 300,
    },
    type: 'Orthogonal',
    style: {
      strokeColor: '#6BA5D7',
    },
    // Sets the Annotation for the Connector
    annotations: [
      {
        // Sets the text to be diaplayed
        content: 'Annotation',
      },
    ],
  };
  
  // initialize Diagram component
  
  var diagram = new ej.diagrams.Diagram(
    {
      width: '100%',
      height: '600px',
      nodes: [node],
      connectors: [connector],
    },
    '#element'
  );
<!DOCTYPE html><html lang="en"><head>
    <title>EJ2 Diagram</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">
    
    <link href="https://cdn.syncfusion.com/ej2/27.2.2/ej2-base/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/27.2.2/ej2-buttons/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/27.2.2/ej2-popups/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/27.2.2/ej2-splitbuttons/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/27.2.2/ej2-diagrams/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/27.2.2/ej2-navigations/styles/fabric.css" rel="stylesheet">
    
<script src="https://cdn.syncfusion.com/ej2/27.2.2/dist/ej2.min.js" type="text/javascript"></script>
<script src="https://cdn.syncfusion.com/ej2/syncfusion-helper.js" type ="text/javascript"></script>
</head>

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

Add annotations at runtime

Annotations can be added at runtime by using the diagram method addLabels. The following code illustrates how to add a annotation to a node.

The annotation’s id property is used to define the name of the annotation and its further used to find the annotation at runtime and do any customization.

index.js
index.html
var node = {
    // Position of the node
    offsetX: 250,
    offsetY: 250,
    // Size of the node
    width: 100,
    height: 100,
    style: { fill: '#6BA5D7', strokeColor: 'white' },
        };

// initialize Diagram component

var diagram = new ej.diagrams.Diagram({
    width: '100%', height: '600px', nodes: [node]
    });
diagram.appendTo('#element');



document.getElementById('addAnnotation').onclick = () => {
    var annotation =  [{ id: 'label1', content: 'Annotation' }]
    //Parameters of addLabels method
    //1. Node - Node to add the annotation
    //2. Annotation - Annotation to be added to the node
    diagram.addLabels(diagram.nodes[0], annotation);
    diagram.dataBind();
};
<!DOCTYPE html><html lang="en"><head>
    <title>EJ2 Diagram</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">
    
    <link href="https://cdn.syncfusion.com/ej2/27.2.2/ej2-base/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/27.2.2/ej2-buttons/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/27.2.2/ej2-popups/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/27.2.2/ej2-splitbuttons/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/27.2.2/ej2-diagrams/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/27.2.2/ej2-navigations/styles/fabric.css" rel="stylesheet">
    
<script src="https://cdn.syncfusion.com/ej2/27.2.2/dist/ej2.min.js" type="text/javascript"></script>
<script src="https://cdn.syncfusion.com/ej2/syncfusion-helper.js" type ="text/javascript"></script>
</head>

<body>
    
    <div id="container">
        <input type="button" value="addAnnotation" id="addAnnotation" />
        <div id="element"></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>

Remove annotation

A collection of annotations can be removed from the node by using diagram method removeLabels. The following code illustrates how to remove a annotation to a node.

index.js
index.html
var node = {
    // Position of the node
    offsetX: 250,
    offsetY: 250,
    // Size of the node
    width: 100,
    height: 100,
    sstyle: { fill: '#6BA5D7', strokeColor: 'white' },
    annotations: [
      {
        id: 'label1',
        content: 'Annotation',
      },
    ],
  };
  
  // initialize Diagram component
  
  var diagram = new ej.diagrams.Diagram(
    {
      width: '100%',
      height: '600px',
      nodes: [node],
    },
    '#element'
  );
  document.getElementById('removeAnnotation').onclick = () => {
    let annotation = diagram.nodes[0].annotations;
    diagram.removeLabels(diagram.nodes[0], annotation);
  };
<!DOCTYPE html><html lang="en"><head>
    <title>EJ2 Diagram</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">
    
    <link href="https://cdn.syncfusion.com/ej2/27.2.2/ej2-base/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/27.2.2/ej2-buttons/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/27.2.2/ej2-popups/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/27.2.2/ej2-splitbuttons/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/27.2.2/ej2-diagrams/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/27.2.2/ej2-navigations/styles/fabric.css" rel="stylesheet">
    
<script src="https://cdn.syncfusion.com/ej2/27.2.2/dist/ej2.min.js" type="text/javascript"></script>
<script src="https://cdn.syncfusion.com/ej2/syncfusion-helper.js" type ="text/javascript"></script>
</head>

<body>
    
    <div id="container">
        <input type="button" value="removeAnnotation" id="removeAnnotation" />
        <div id="element"></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>

Update annotation at runtime

You can get the annotation directly from the node’s annotations collection property and you can change any annotation properties at runtime. To reflect the changes immediately, we need to call dataBind.

The following code example illustrates how to change the annotation properties.

index.js
index.html
var node = {
    // Position of the node
    offsetX: 250,
    offsetY: 250,
    // Size of the node
    width: 100,
    height: 100,
    sstyle: { fill: '#6BA5D7', strokeColor: 'white' },
    annotations: [{ content: 'Annotation' }],
  };
  
  // initialize Diagram component
  
  var diagram = new ej.diagrams.Diagram(
    {
      width: '100%',
      height: '600px',
      nodes: [node],
    },
    '#element'
  );
  
  document.getElementById('updateAnnotation').onclick = () => {
    diagram.nodes[0].annotations[0].content = 'Updated Annotation';
    diagram.dataBind();
  };
<!DOCTYPE html><html lang="en"><head>
    <title>EJ2 Diagram</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">
    
    <link href="https://cdn.syncfusion.com/ej2/27.2.2/ej2-base/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/27.2.2/ej2-buttons/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/27.2.2/ej2-popups/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/27.2.2/ej2-splitbuttons/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/27.2.2/ej2-diagrams/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/27.2.2/ej2-navigations/styles/fabric.css" rel="stylesheet">
    
<script src="https://cdn.syncfusion.com/ej2/27.2.2/dist/ej2.min.js" type="text/javascript"></script>
<script src="https://cdn.syncfusion.com/ej2/syncfusion-helper.js" type ="text/javascript"></script>
</head>

<body>
    
    <div id="container">
        <input type="button" value="updateAnnotation" id="updateAnnotation" />
        <div id="element"></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>