Ways to create a Set in JavaScript?

Question

In Eloquent JavaScript, Chapter 4, a set of values is created by creating an object and storing the values as property names, assigning arbitrary values (e.g. true) as property

Answer 1

I use dict objects as sets. This works with strings and numbers, but I suppose would cause problems if you wanted to have a set of objects using custom equality and comparison operators:

Creating a set:

var example_set = 
{
    'a':true,
    'b':true,
    'c':true
}

Testing for inclusion in a set

if( example_set['a'] ){
    alert('"a" is in set');
}

Adding an element to a set

example_set['d'] = true;

Removing an element from a set

delete example_set['a'];