The set.empty() function in D3.js is used to return true if the given array has zero elements otherwise returns false.
Syntax:
d3.set([Array]).empty();
Parameters: This function accepts single parameter Array which is going to be searched whether it is empty or not.
Return Value: It returns true if the given array is empty otherwise returns false.
Below programs illustrate the d3.set.empty() function in D3.js:
Example 1:
<!DOCTYPE html> <html>   <head>     <title>         d3.set.empty() function     </title>       </head>   <body>     <script>                // Initialising an array          Array1 = [ "a" ];          Array2 = [];          Array3 = [ "Geeks" , "gfg" , "neveropen" ];                      // Calling the d3.set.empty() function          A = d3.set(Array1).empty();          B = d3.set(Array2).empty();          C = d3.set(Array3).empty();                      // Getting the value true if the given array is          // empty otherwise returns false          console.log(A);          console.log(B);          console.log(C);     </script> </body>   </html>                    |
Output:
false true false
Example 2:
<!DOCTYPE html> <html>   <head>     <title>         d3.set.empty() function     </title>       </head>   <body>     <script>               // Calling the d3.set.empty() function         // with a array as the parameter         A = d3.set([1, 2, 3, 3]).empty();         B = d3.set([]).empty();         C = d3.set([ "a" , "b" , "c" , "a" , "b" , "c" ]).empty();                 // Getting the value true if the given array is         // empty otherwise returns false         console.log(A);         console.log(B);         console.log(C);     </script> </body>   </html>                    |
Output:
false true false
Ref: https://devdocs.io/d3~5/d3-collection#set_empty