Using Sets for Uniqueness

TODO: collapasable, copyable, download, etc

For vanilla code that runs in the browser, how do you use a Set so that you can be sure a collection of items are unique?Using a Set in vanilla JavaScript (that is, JavaScript without any additional libraries or frameworks) is an efficient way to ensure a collection of items is unique. A Set is a built-in object that stores unique values of any type, whether primitive values or object references.

Here's how you can use a Set to ensure uniqueness in a collection:

1. Creating a Set: You can create a new Set by simply calling its constructor.

   let mySet = new Set();
   

2. Adding Items: To add items to the Set, use the .add() method. If you try to add a duplicate item, the Set will simply ignore it.

   mySet.add("apple");
   mySet.add("banana");
   mySet.add("apple"); // This will not be added again
   

3. Checking for Existence: You can check if an item is in the Set using the .has() method.

   if (mySet.has("banana")) {
       // Item exists in the set
   }
   

4. Removing Items: To remove an item, use the .delete() method.

   mySet.delete("banana"); // Removes "banana" from the set
   

5. Iterating Over a Set: You can iterate over the elements of a Set using for...of loop or .forEach() method.

   for (let item of mySet) {
       console.log(item);
   }
   
   // or
   
   mySet.forEach(function(item) {
       console.log(item);
   });
   

6. Converting a Set to an Array: If you need to convert the Set back to an array, you can use the spread operator or Array.from().

   let myArray = [...mySet];
   // or
   let myArray = Array.from(mySet);
   

7. Getting the Size of a Set: Use the .size property to find out how many items are in the Set.

   console.log(mySet.size);
   

Here's a simple example that combines these steps:

let mySet = new Set();

mySet.add("apple");
mySet.add("banana");
mySet.add("orange");

console.log("Does my set have an apple?", mySet.has("apple")); // true

mySet.delete("banana");

for (let fruit of mySet) {
    console.log(fruit);
}

// Output:
// Does my set have an apple? true
// apple
// orange

This example demonstrates how Set ensures that each item is unique and provides various methods to manipulate and query the set.

Using Sets for Uniqueness created at Tue Jan 20 1970 17:57:11 GMT+0000 (Coordinated Universal Time)