join - nodef/extra-set GitHub Wiki
Join values together into a string.
function join(x, sep)
// x: a set
// sep: separator [,]
const set = require('extra-set');
var x = new Set([1, 2, 3]);
set.join(x);
// → "1,2,3"
set.join(x, ", ");
// → "1, 2, 3"