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 - <a href="./hoisting.md">Hoisting</a>
 - <a href="./call-by-value-and-call-by-reference.md">Call by value and call by reference</a>
 - <a href="./array-string-methods.md">Array and String methods</a>
-- <a href="./date-object.md">Date Object and methods</a>
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+- <a href="./date-object.md">Date Object and methods</a>
+- <a href="./set-and-weakset.md">Sets and WeakSets</a>
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diff --git a/set-and-weakset.md b/set-and-weakset.md
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+# **Sets and Weaksets**
+Sets and Weaksets are Javascript build-in objects used for storing values.
+
+## Sets
+The **`Set`** object lets you store **unique** values of any type, whether [primitive values](https://developer.mozilla.org/en-US/docs/Glossary/Primitive) or object references.
+
+> There are 7 primitive data types:
+> [string](https://developer.mozilla.org/en-US/docs/Glossary/String),
+> [number](https://developer.mozilla.org/en-US/docs/Glossary/Number),
+> [bigint](https://developer.mozilla.org/en-US/docs/Glossary/BigInt),
+> [boolean](https://developer.mozilla.org/en-US/docs/Glossary/Boolean),
+> [undefined](https://developer.mozilla.org/en-US/docs/Glossary/undefined),
+> [symbol](https://developer.mozilla.org/en-US/docs/Glossary/Symbol),
+>  [null](https://developer.mozilla.org/en-US/docs/Glossary/Null).
+
+You can iterate through the elements of a set in insertion order.
+
+> Set is used to create mathematical set operation like uinion,intersection etc
+
+### Set Methods
+
+ 1. **Set.add(value)**
+	Appends  `value`  to the  `Set`  object. Returns the  `Set`  object with added value.
+
+ 2. **Set.clear()**
+	Removes all elements from the  `Set`  object.
+
+ 3. **Set.delete(value)**
+	Removes the element associated to the  `value`  and returns a boolean  whether an element was successfully removed or not.  
+
+ 4. **Set.has(value)**
+	 Returns a boolean asserting whether an element is present with the given value in the  `Set`  object or not.
+
+**Example usage**
+```
+const mySet1 = new Set()
+
+mySet1.add(1)           // Set [ 1 ]
+mySet1.add(5)           // Set [ 1, 5 ]
+mySet1.add(5)           // Set [ 1, 5 ]
+mySet1.add('some text') // Set [ 1, 5, 'some text' ]
+const o = {a: 1, b: 2}
+mySet1.add(o)
+
+mySet1.add({a: 1, b: 2})   // o is referencing a different object, so this is okay
+
+mySet1.has(1)              // true
+mySet1.has(3)              // false, since 3 has not been added to the set
+mySet1.has(5)              // true
+mySet1.has(Math.sqrt(25))  // true
+mySet1.has('Some Text'.toLowerCase()) // true
+mySet1.has(o)       // true
+
+mySet1.size         // 5
+
+mySet1.delete(5)    // removes 5 from the set
+mySet1.has(5)       // false, 5 has been removed
+
+mySet1.size         // 4, since we just removed one value
+
+console.log(mySet1)
+// logs Set(4) [ 1, "some text", {…}, {…} ] in Firefox
+// logs Set(4) { 1, "some text", {…}, {…} } in Chrome
+```
+**Set Iteration**
+```
+// iterate over items in set
+// logs the items in the order: 1, "some text", {"a": 1, "b": 2}, {"a": 1, "b": 2}
+for (let item of mySet1) console.log(item)
+
+```
+
+### Set Tricks
+
+>You can easily convert a set to an array by using a [`spread operator`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Spread_syntax)
+```
+const array = [...new Set([1, 2, 3, 4])];
+console.log(array)
+// [1, 2, 3, 4]
+
+```
+>Since set only contains unique values it can be used to remove duplicates.
+
+```
+
+const numbers = [2,3,4,4,2,3,3,4,4,5,5,6,6,7,5,32,3,4,5]
+
+console.log([...new Set(numbers)])
+
+// [2, 3, 4, 5, 6, 7, 32]
+
+```
+## Weakset
+
+`WeakSet` objects are collections of **objects**. Just as with `Set`, each object in a `WeakSet` may occur only once; all objects in a `WeakSet`'s collection are unique.
+The `WeakSet` is weak, meaning references to objects in a `WeakSet` are held weakly.
+>This also means that there is no list of current objects stored in the collection. `WeakSets` are not enumerable.
+>WeaSets are not Iteratable
+
+
+### WeakSet Methods
+
+ 1. **WeakSet.add(value)**
+	Appends  `value`  to the  `WeakSet`  object. Returns the  `WeakSet`  object with added value.
+
+ 2. **WeakSet.delete(value)**
+	Removes the element associated to the  `value`  and returns a boolean  whether an element was successfully removed or not.  
+
+ 3. **WeakSet.has(value)**
+	 Returns a boolean asserting whether an element is present with the given value in the  `WeakSet`  object or not.
+ 
+ **Example usage**
+		
+		const ws = new WeakSet();
+		const foo = {};
+		const bar = {};
+		ws.add(foo);
+		ws.add(bar);
+		ws.has(foo);    // true
+		ws.has(bar);    // true
+		ws.delete(foo); // removes foo from the set
+		ws.has(foo);    // false, foo has been removed
+		ws.has(bar);    // true, bar is retained
+		
+
+
+# Conclusion
+
+-   Sets can store any value. WeakSets are collections of objects only.
+-   WeakSet does not have  _size_  property.
+-   WeakSet does not have  _clear, keys, values, entries, forEach_  methods.
+-   WeakSet is not iterable.
+## For more information
+
+https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set
+
+https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WeakSet
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