D3.js node.count()函数

D3.js库的node.count()函数用于计算特定节点下的叶子数，并将其作为值属性附加到对象。如果给定的节点本身是叶节点，则计数为 1。

句法：

node.count();

参数：此函数不带任何参数。

返回值：此函数返回一个对象。

下面给出了上面给出的函数的几个例子。

示例 1：以下示例演示了计算根节点的叶子。

HTML

  

    
    
  
    
    

  

    
        // 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);
    

  

输出：

示例 2：以下代码演示了计算任何节点的叶子数。

HTML

  

    
    
    
    

  

    
        // 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);
    

  

输出：