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