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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



Last Updated : 28 Jun, 2019
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