JavaScript Sets
A JavaScript Set is a collection of unique values.
Each value can only occur once in a Set.
Essential Set Methods
| Method | Description |
|---|---|
| new Set() | Creates a new Set |
| add() | Adds a new element to the Set |
| delete() | Removes an element from a Set |
| has() | Returns true if a value exists in the Set |
| forEach() | Invokes a callback for each element in the Set |
| values() | Returns an iterator with all the values in a Set |
| Property | Description |
| size | Returns the number of elements in a Set |
How to Create a Set
You can create a JavaScript Set by:
- Passing an Array to
new Set() - Create a new Set and use
add()to add values - Create a new Set and use
add()to add variables
The new Set() Method
Pass an Array to the new Set() constructor:
Create a Set and add values:
Example
// Create a Set
const letters = new Set();
// Add Values to the Set
letters.add("a");
letters.add("b");
letters.add("c");
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Create a Set and add variables:
Example
// Create a Set
const letters = new Set();
// Create Variables
const a = "a";
const b = "b";
const c = "c";
// Add Variables to the Set
letters.add(a);
letters.add(b);
letters.add(c);
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The add() Method
If you add equal elements, only the first will be saved:
Example
letters.add("a");
letters.add("b");
letters.add("c");
letters.add("c");
letters.add("c");
letters.add("c");
letters.add("c");
letters.add("c");
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The forEach() Method
The forEach() method invokes (calls) a function for each Set element:
Example
// Create a Set
const letters = new Set(["a","b","c"]);
// List all Elements
let text = "";
letters.forEach (function(value) {
text += value;
})
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The values() Method
The values() method returns a new iterator object containing all the values in a Set:
Now you can use the Iterator object to access the elements:
Example
// List all Elements
let text = "";
for (const x of letters.values()) {
text += x;
}
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