The JavaScript Set object is used to store the elements with unique values. The values can be of any type i.e. whether primitive values or object references.
iterable - It represents an iterable object whose elements will be added to the new Set.
A Set
is a special type collection – “set of values” (without keys), where each value may occur only once.
Its main methods are:
new Set(iterable)
– creates the set, and if an iterable
object is provided (usually an array), copies values from it into the set.set.add(value)
– adds a value, returns the set itself.set.delete(value)
– removes the value, returns true
if value
existed at the moment of the call, otherwise false
.set.has(value)
– returns true
if the value exists in the set, otherwise false
.set.clear()
– removes everything from the set.set.size
– is the elements count.The main feature is that repeated calls of set.add(value)
with the same value don’t do anything. That’s the reason why each value appears in a Set
only once.
For example, we have visitors coming, and we’d like to remember everyone. But repeated visits should not lead to duplicates. A visitor must be “counted” only once.