The set.add() function in D3.js is used to add the specified value string to the created set.
Syntax:
d3.set().add(element);
Parameters: This function accepts single parameter element which is going to be added into the created set.
Return Value: This function does not returns any values.
Below programs illustrate the d3.set.add() function in D3.js:
Example 1:
<!DOCTYPE html>   <html>    <head>     <title> d3.set.add() Function</title>    </head>   <body>   <script>            // Initialising the set      var set = d3.set()     .add( "Geeks" )     .add( "Geeks" )     .add( "gfg" );       // Checking whether the desired element is     // present or not     A = set.has( "neveropen" );     B = set.has( "Ram" );     C = set.has( "Geeks" );           // Getting the output of true or false     console.log(A);     console.log(B);     console.log(C);   </script> </body>   </html> |
Output:
false false true
Example 2:
<!DOCTYPE html>   <html>    <head>     <title> d3.set.add() Function</title>    </head>   <body>   <script>            // Initialising the set      var set = d3.set().add( "a" ).add(1).add(123);       // Checking whether the desired element is     // present or not     A = set.has( "a" );     B = set.has(123);     C = set.has(5);           // Getting the output of true or false     console.log(A);     console.log(B);     console.log(C);   </script> </body>   </html> |
Output:
true true false
Ref: https://devdocs.io/d3~5/d3-collection#set_add