JavaScript Sets
A JavaScript Set is a collection of unique values.
Each value can only occur once in a Set.
The values can be of any type, primitive values or objects.
How to Create a Set
You can create a JavaScript Set by:
- Passing an array to
new Set() - Create an empty set and use
add()to add values
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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Listing the Elements
You can list all Set elements (values) with a for..of loop:
Example
// Create a Set
const letters = new Set(["a","b","c"]);
// List all Elements
let text = "";
for (const x of letters) {
text += x;
}
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Sets are Objects
typeof returns object:
typeof letters; // Returns object
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instanceof Set returns true:
letters instanceof Set; // Returns true
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Complete Set Reference
For a complete reference, go to our:
Complete JavaScript Set Reference.
The reference contains descriptions and examples of all Set Properties and Methods.
Browser Support
Set is an ES6 feature (JavaScript 2015).
ES6 is fully supported in all modern browsers since June 2017:
| Chrome 51 | Edge 15 | Firefox 54 | Safari 10 | Opera 38 |
| May 2016 | Apr 2017 | Jun 2017 | Sep 2016 | Jun 2016 |
Set is not supported in Internet Explorer.
