Using Set in JavaScript
04 Jul, 2019What is Set in JavaScript?
Set lets you store unique object references or primitive values.
Let’s start with an example:
1. Using primitive values
const numbers = new Set([1,2,3,3]);
for(let number of numbers) {
console.log(number );
}
//1
//2
//3const strings = new Set(['1','2','3','3']);
for(let string of strings) {
console.log(string );
}
//'1'
//'2'
//'3'What we illustrated above is just a simple usecase where we have primitive values and we need those values to be unique, creating a set is the simplest way to do it.
In the next example we will look at how we can make a set with unique objects references:
2. Using object references
const person = {
name: 'Allan'
};
const person2 = {
name: 'Jhon'
};
const persons = new Set([person, person, person, person2]);
for(let person of persons) {
console.log(person.name);
}
//"Allan"
//"Jhon"As you might seen we’ve created a new set with 4 persons, but the object was the same (reference) and therefor it was removed from our collection.
In the last example we will look at how we can make a collection of unique objects based on a particular property that all objects are sharing:
3. Unique objects based on a property name
const person = {
name: 'Allan'
};
const person2 = {
name: 'Allan'
};
const person3 = {
name: 'Jhon'
};
const persons = [person, person, person, person2, person3, person3];
const uniqByName = [];
const tempSet = new Set();
for (const person of persons) {
if(!tempSet.has(person.name)){
tempSet.add(person.name);
uniqByName.push({
name: person.name
});
}
}
console.log(uniqByName);
//[[object Object] {
name: "Allan"
}, [object Object] {
name: "Jhon"
}]Using the Set object we were able to build a much more nicer and cleaner way to create an array with unique object based on some random property.
Read more on sets here.
