D3.js | d3.map.keys() Function

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The map.keys() function in D3.js is used to return an array of string keys for every entry in the created map. The order of the returned keys is arbitrary.

Syntax:

map.keys()

Parameters: This function does not accept any parameters.

Return Value: This function returns an array of string keys for every entry in the created map.

Below programs illustrate the d3.map.keys() function in D3.js:

Example 1:

<!DOCTYPE html> 
<html> 
  
<head> 
    <title>d3.map.keys() function</title> 
  
    <script src='https://d3js.org/d3.v4.min.js'></script> 
</head> 
  
<body> 
    <script> 
          
        // Creating a map 
        var map = d3.map({"Ram": 5, "Geeks": 10, "gfg": 15}); 
        
        // Calling the map.keys() function 
        A = map.keys(); 
        
        // Getting an array of string keys for 
        // every entry in the map. 
        console.log(A); 
    </script> 
</body> 
  
</html> 

Output:

["Ram", "Geeks", "gfg"]

Example 2:

<!DOCTYPE html> 
<html> 
  
<head> 
    <title>d3.map.keys() function</title> 
  
    <script src='https://d3js.org/d3.v4.min.js'></script> 
</head> 
  
<body> 
    <script> 
          
        // Creating some maps 
        var map1 = d3.map({"Ram": 5}); 
        var map2 = d3.map({"Geeks": 10}); 
        var map3 = d3.map({"Ram": 5, "Geeks": 10}); 
        var map4 = d3.map(); 
        
        // Calling the map.keys() function 
        A = map1.keys(); 
        B = map2.keys(); 
        C = map3.keys(); 
        D = map4.keys(); 
        
        // Getting an array of string keys for 
        // every entry in the map. 
        console.log(A); 
        console.log(B); 
        console.log(C); 
        console.log(D); 
    </script> 
</body> 
  
</html> 

Output:

["Ram"]
["Geeks"]
["Ram", "Geeks"]
[]

Ref: https://devdocs.io/d3~5/d3-collection#map_keys

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