D3.js node.leaves() Function

Last Updated : 23 Sep, 2020

The node.leaves() function in d3.js is used to return an array of leaf nodes of the given hierarchical data in traversal order.

Syntax:

node.leaves();

Parameters: This function does not accept any parameters.

Return Values: This function return an array.

Note: Leaf nodes are those nodes which have no children.

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

Example 1:

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_leaf1" 
                }, 
                { 
                    name: "child2", 
                    children: [ 
                        { 
                            name: "grandchild1", 
                            children: [ 
                                { name: "leaf2" } 
                            ] 
                        }, 
                    ] 
                }, 
                { 
                    name: "child3", 
                    children: [ 
                        { name: "leaf3" }, 
                        { name: "leaf4" }, 
                    ] 
                } 
            ] 
        }; 
  
        var obj = d3.hierarchy(tree); 
          
        // Leaf nodes of the above given tree 
        console.log("Leaf nodes are: "); 
        console.log(obj.leaves());         
    </script> 
</body> 
  
</html> 

Output:

Example 2: The following code demonstrates accessing data of leaf nodes.

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_leaf1" 
                }, 
                { 
                    name: "child2", 
                    children: [ 
                        { 
                            name: "grandchild1", 
                            children: [ 
                                { name: "leaf2" } 
                            ] 
                        }, 
                    ] 
                }, 
                { 
                    name: "child3", 
                    children: [ 
                        { name: "leaf3" }, 
                        { name: "leaf4" }, 
                    ] 
                } 
            ] 
        }; 
  
        var obj = d3.hierarchy(tree); 
          
        // Leaf nodes of the above given tree are: 
        console.log(" Accessing Leaf nodes: "); 
        let leafArr = obj.leaves(); 
        leafArr.forEach((e) => { 
            console.log(e.data); 
            console.log("depth: ", e.depth); 
        })         
    </script> 
</body> 
  
</html> 