JS: Set.prototype.add

New in JS2015.

setObj.add(value)

Add value to the set setObj.

Return the modified set.

// create a set, add value to it
const s = new Set();

s.add (6);
s.add (5);
s.add (6);

// the set is modified
console.log(s);
// Set { 6, 5 }

console.log( s.add (7));
// Set { 6, 5, 7 }
// the method “add” returns the modified set