D3.js node.sum() Function

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The node.sum() function in d3.js is used to evaluate the specified value function for a particular node. The node.value property of this function contains the value returned by the specified function.

Syntax:

node.sum(value);

Parameters: This function accepts a single parameter as mentioned above and described below:

value: This takes a function to be evaluated for each node.

Return Values: This function returns an object.

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", // Root node 
            children: [ 
                { 
                    name: "child1", // Child of root node 
                    value: 2 
                }, 
                { 
                    name: "child2", // Child of root node 
                    value: 3, 
                    children: [ 
                        { 
                            name: "grandchild1", // Child of child2 
                            value: 1, 
                            children:[ 
                                {name: "grand_granchild1_1",value: 4},                               
                                // Child of grandchild1 
                                {name: "grand_granchild1_2",value: 5}                      
                               // Child of grandchild1 
                            ] 
                        }, 
                        { 
                            name: "grandchild2", 
                            children:[ 
                                {name: "grand_granchild2_1"},   
                                // Child of grandchild2 
                                {name: "grand_granchild2_2"}   
                                // Child of grandchild2 
                            ] 
                        }, 
                    ] 
                } 
            ] 
        }; 
  
        var obj = d3.hierarchy(tree); 
        var grandchild2=obj.children[1].children[1]; 
          
        var sum=obj.sum(d=>d.value); 
        console.log(sum); 
        console.log("The sum of value is: ",sum.value); 
    </script>  
</body>  
</html> 

Output:

Example 2:

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: [ 
                {value:1}, 
                {value:2}, 
                {value:3}, 
                {value:4}, 
                {value:5}, 
                {value:6}, 
            ] 
        }; 
  
        var obj = d3.hierarchy(tree); 
          
        var sum=obj.sum(d=>d.value*12); 
        // 1 + 2 + 3 + 4 + 5 + 6 = 21*12=252 
        console.log(sum); 
        console.log("The value is: ",sum.value); 
    </script>  
</body>  
</html> 

Output:

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