D3.js stack.value() Method

Last Updated : 18 Sep, 2020

The stack.value() method takes a function that returns the value associated with a key.

Syntax:

stack.value([value_func])

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

value_func: This is a function returning the value associated with the key.

Return Value: This method has no return value.

Example:

HTML

<!DOCTYPE html> 
<html> 
  
<head> 
    <meta charset="utf-8"> 
    <script src= 
        "https://d3js.org/d3.v5.min.js"> 
    </script> 
</head> 
  
<body> 
    <h1 style="text-align:center; color:green;"> 
        GeeksforGeeks 
    </h1> 
  
    <center> 
        <canvas id="gfg" width="200" height="200"> 
        </canvas> 
    </center> 
  
    <script> 
        var data = [ 
            { letter: { a: 3840, b: 1920, c: 960, d: 400 } }, 
            { letter: { a: 1600, b: 1440, c: 960, d: 400 } }, 
            { letter: { a: 640, b: 960, c: 640, d: 400 } }, 
            { letter: { a: 320, b: 480, c: 640, d: 400 } } 
        ]; 
  
        var stackGen = d3.stack() 
            // Defining keys 
            .keys(["a", "b", "c", "d"]) 
            // Defining value function 
            .value((obj, key) => obj.letter[key]); 
  
        var stack = stackGen(data); 
  
        console.log(stack); 
    </script> 
</body> 
  
</html> 