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> </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> </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:
