D3.js stack.keys() Method

Last Updated : 07 Sep, 2020

The stack.keys() method makes an array of strings as an argument and returns the stack generator.

Syntax:

 stack.keys([keys])

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

domain: This parameter holds an array of strings as key arguments.

Return Value: This method returns the stack generator.

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 = [ 
              {a: 3840, b: 1920, c: 960, d: 400}, 
              {a: 1600, b: 1440, c: 960, d: 400}, 
              {a:  640, b:  960, c: 640, d: 400}, 
              {a:  320, b:  480, c: 640, d: 400} 
            ]; 
  
        var stackGen = d3.stack() 
            // Defining keys 
            .keys(["a", "b", "c", "d"]) 
  
        var stack = stackGen(data); 
          
        console.log(stack); 
  
        for (i = 0; i < 4; i++) { 
  
            // Displaying keys 
            console.log(stack[i].key);    
        } 
    </script> 
</body> 
</html> 