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D3.js node.count() Function

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  • Last Updated : 23 Sep, 2020

The node.count() function of D3.js library is used to count the number of leaves under a particular node and append it as a value property to the object. If the node given is itself a leaf node then the count is one.

Syntax:

node.count();

Parameters: This function does not take any parameter.

Return Value: This function returns an object.

Below given are a few examples of the function given above.

Example 1: The following example demonstrates counting leaves for the root node.

HTML




<!DOCTYPE html>
<html lang="en">
  
<head>
    <meta charset="UTF-8" />
    <meta name="viewport" path1tent=
    "width=device-width, initial-scale = 1.0" />
  
    <script src="https://d3js.org/d3.v4.min.js">
    </script>
</head>
  
<body>
    <script>
        // Constructing a tree
        var tree = {
            name: "rootNode",
            children: [
                {
                    name: "child1"
                },
                {
                    name: "child2",
                    children: [
                        {
                            name: "grandchild1",
                            children: [
                                { name: "grand_granchild1_1" },
                                { name: "grand_granchild1_2" }
                            ]
                        },
                        {
                            name: "grandchild2",
                            children: [
                                { name: "grand_granchild2_1" },
                                { name: "grand_granchild2_2" }
                            ]
                        },
                    ]
                }
            ]
        };
  
        var obj = d3.hierarchy(tree);
  
        // Using node.count() Function
        var count = obj.count();
        console.log("The number of leaves for root"
                + " node are: ", count.value);
    </script>
</body>
  
</html>

Output:

Example 2: The following code demonstrates counting number of leaves for any node.

HTML




<!DOCTYPE html>
<html lang="en">
  
<head>
    <meta charset="UTF-8" />
    <meta name="viewport" path1tent=
        "width=device-width, initial-scale = 1.0" />
    <script src="https://d3js.org/d3.v4.min.js">
    </script>
</head>
  
<body>
    <script>
        // Constructing a tree
        var tree = {
            name: "rootNode", // Root node
            children: [
                {
                    name: "child1" // Child of root node
                },
                {
                    name: "child2", // Child of root node
                    children: [
                        {
                            // Child of child2
                            name: "grandchild1",
                            children: [
                                // Child of grandchild1
                                { name: "grand_granchild1_1" },
                                // Child of grandchild1 
                                { name: "grand_granchild1_2" }
                            ]
                        },
                        {
                            name: "grandchild2",
                            children: [
                                // Child of grandchild2
                                { name: "grand_granchild2_1" },
                                // Child of grandchild2
                                { name: "grand_granchild2_2" }
                            ]
                        },
                    ]
                }
            ]
        };
  
        var obj = d3.hierarchy(tree);
        var grandchild2 = obj.children[1].children[1];
  
        // Using node.count() function
        var count = grandchild2.count();
        console.log("The number of leaves for "
            + "grandchild2 are: ", count.value);
    </script>
</body>
  
</html>

Output:


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