Sets

Set is a collection containing only unique elements.

Sets are not supported by older browsers such as internet explorer.

Creation

Empty Set

let emptySet = new Set();

Initial Values

let names = new Set(["John", "Smith", "Alex"]);

Inserting Data

Insertion is done via the add function. Like in the following example:

let cities = new Set(); cities.add("Tokyo"); cities.add("Chicago"); cities.add("Tokyo"); cities.add("Madrid"); console.log(cities);

Output:

Set(3) {"Tokyo", "Chicago", "Madrid"}

Notice that Tokyo is contained only once, since no duplicates are allowed.

Size

Size is the count of Set's elements. It's accessed via the size property.

let names = new Set(); names.add("John"); names.add("Smith"); names.add("Smith"); names.add("Bell"); console.log(names.size);

Output:

3

Remove Element

Certain values can be removed via the delete function.

var names = new Set(); names.add("Emily"); names.add("Lily"); names.add("Teo"); names.delete("Teo"); console.log(names);

Output:

Set(2) {"Emily", "Lily"}

Contains

A value can be checked if contained via the has method.

let names = new Set(); names.add("Leo"); names.add("Shone"); names.add("Alice"); console.log(names.has("Shone"));

Output:

true

Loop Through

It can be iterated via forEach:

var makes = new Set(); makes.add("Volvo"); makes.add("Ford"); makes.add("Audi"); makes.forEach(function(make) { console.log(make); });

Output:

Volvo Ford Audi