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> </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> </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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