Sets
The Set is a new object type provided by ES6. It is nothing but a collection of values, which are unique. The values can be either simple primitives such as strings, integers etc. or complex object types such as object literals or arrays.
Syntax
new Set([iterable]);
parameters
iterable
It is an iterable object whose elements will be added to the new set. In case if the iterable is not provided or a null value is passed then the new set will be empty.
Example
Since a set allows only unique values, the length of the object after adding some of existing elements in the set will not be changed.
<html>
<body>
<script>
var set1 = new Set(["a","a","b","b","c"]);// no of unique elements - 3(a, b and c)
set1.add('c').add('d') // Two elements were added (c,d)
set1.forEach(alphabet => { // In total 7 elements but only 4 unique values
document.write(`alphabet ${alphabet}!`);
document.write("</br>");
});
document.write(set1.size); // it displays 4 since sets accept only unique values.
</script>
</body>
</html>Output
alphabet a! alphabet b! alphabet c! alphabet d! 4
Example-2
Sets also display boolean value. They check whether a provided element is available or not in the given set and executes a boolean output.
<html>
<body>
<script>
var set1 = new Set(["a","a","b","b","c"]);
set1.add('c').add('d')
set1.forEach(alphabet => {
document.write(`alphabet ${alphabet}!`);
document.write("</br>");
});
document.write(set1.has('a')); // it display true because a is there in set1
document.write("</br>");
document.write(set1.has('8')); // it display false because there is no 8 in the set1.
document.write("</br>");
document.write(set1.size); // displays only unique values because only unique values are accepted
</script>
</body>
</html>Output
alphabet a! alphabet b! alphabet c! alphabet d! true false 4