Adding object source code and practice questions

Vishal-raj-1 · Vishal-raj-1 · commit 5c85aefa402e · 2023-08-17T15:13:08.000+05:30
diff --git a/Objects/README.md b/Objects/README.md
@@ -0,0 +1,185 @@
+# Objects in JavaScript
+
+<p align="center">
+  <a href="https://youtube.com/live/pYTNGZERlQY">
+  <img src="https://img.youtube.com/vi/pYTNGZERlQY/0.jpg" alt="Objects In JavaScript" />
+  </a>
+</p>
+
+### Creating an object
+```javascript
+const person = {
+    name: "Vishal",
+    age: 21,
+    isEducator: true,
+    skills: ["C++", "JavaScript", "ReactJS"],
+    projects: {
+        "Frontend Freaks": "Frontend Development Project",
+    },
+    code: function(){
+        return "start coding";
+    },
+    walk: () => {
+        return "start walking";
+    }
+}
+```
+
+### Accessing properties using Dot Operator
+```javascript
+console.log(person.age); // 21
+```
+
+### Accessing properties using []
+```javascript
+console.log(person["name"]); // Vishal
+```
+
+### Checking if a key exists in the object
+```javascript
+console.log(person.hasOwnProperty("name")) // true
+console.log(person.hasOwnProperty("last Name")) // false
+```
+
+### Adding, deleting, and updating keys
+```javascript
+person.name = "Vivek" // Updating name key 
+person.location = "New Delhi" // Adding location Key
+delete person.projects // Deleting projects key
+console.log(person);
+```
+
+### Shallow Copy
+```javascript
+const person2 = person
+person2.isEducator = false;
+```
+
+### Deep Copy
+```javascript
+const person3 = Object.assign({}, person)
+// Nested Objects still do shallow copy here, there for we use lodash cloneDeep method(out of scope for this course)
+person3.skills = null;
+```
+
+### Using freeze and seal methods
+```javascript
+Object.freeze(person) // User can't add or delete or update keys
+console.log(person);
+console.log(Object.isFrozen(person)) // true
+```
+
+```javascript
+Object.seal(person) // User can't add or delete keys but can update the value
+console.log(Object.isSealed(person)); // true
+```
+
+### Keys, Values & Entries
+```javascript
+console.log(Object.keys(person)) // ["name" , "age", "isEducator", ...]
+console.log(Object.values(person)) // ["Vishal", 21, true, ...]
+console.log(Object.entries(person)) // [["name", "Vishal"], ["age", 21], ["isEducator", true], ...]
+```
+
+### Looping through an Object using for...in
+```javascript
+for (let key in person) {
+    console.log(key + ":", person[key]); // name: Vishal   age: 21, isEducator: true ...
+}
+```
+
+### Looping through an Object using forEach with Object.keys
+```javascript
+Object.keys(person).forEach((key) => console.log(key))
+```
+### How to check if two objects are equal?
+```javascript
+console.log(Object.is(person, person3))
+```
+
+### find count of all players
+```javascript
+const data = {
+    id: 1,
+    name: ["P1", "P4"],
+    next: {
+        id: 2,
+        name: ["P3"],
+        next: {
+            id: 3,
+            name: ["P3", "P4", "P5"],
+            next: {
+                id: 4,
+                name: ["P1", "P2", "P4"],
+                next: {
+                    id: 5,
+                    name: ["P2", "P3", "P5"],
+                    next: null
+                }
+            }
+        }
+    }
+};
+
+const playerCount = (data) => {
+    if(data === null){
+        return {}
+    }
+
+    let countPlayer = {}
+    for(let player of data.name){
+        countPlayer[player] = (countPlayer[player] || 0) + 1;
+    }
+    const nextPlayerCount = playerCount(data.next);
+
+    for(let key in nextPlayerCount){
+        countPlayer[key] = (countPlayer[key] || 0) + nextPlayerCount[key]
+    }
+    return countPlayer;
+}
+
+const countPlayer = playerCount(data);
+console.log(countPlayer) // {p1: 2, p4: 3, p3: 3, p2: 2: p5: 2}
+```
+
+### Prototype and Inheritance in JavaScript Objects
+
+```javascript
+const obj1 = {
+    name: "Vishal"
+}
+
+const obj2 = {
+    age: 21,
+    __proto__: obj1
+}
+
+console.log(obj2.name);
+```
+
+### Question 2: Group Anagrams (LeetCode 49)
+
+```javascript
+let anagrams = {};
+    for (let i = 0; i < strs.length; i++) {
+        const str = strs[i].split("").sort().join("")
+        if (!anagrams.hasOwnProperty(str)) {
+            anagrams[str] = []
+        }
+
+        anagrams[str] = [...anagrams[str], strs[i]];
+    }
+    return Object.values(anagrams);
+```
+
+## Practice Questions
+
+1. [Number of Good Pairs](https://leetcode.com/problems/number-of-good-pairs/)
+2. [Count the Number of Consistent Strings](https://leetcode.com/problems/count-the-number-of-consistent-strings/)
+3. [Two Sum](https://leetcode.com/problems/two-sum/)
+4. [Sum of Unique Elements](https://leetcode.com/problems/sum-of-unique-elements/)
+5. [Unique Number of Occurrences](https://leetcode.com/problems/unique-number-of-occurrences/)
+6. [Integer to Roman](https://leetcode.com/problems/integer-to-roman/)
+7. [Longest Substring Without Repeating Characters](https://leetcode.com/problems/longest-substring-without-repeating-characters/)
+8. [Group Anagrams](https://leetcode.com/problems/group-anagrams/)
+9. [Find All Anagrams in a String](https://leetcode.com/problems/find-all-anagrams-in-a-string/)
diff --git a/README.md b/README.md
@@ -28,4 +28,5 @@
 - [Polyfill of Map, Filter & Reduce](https://github.com/Vishal-raj-1/DSA-In-JS-With-Vishal/blob/main/Array/Polyfill.md)
 - [String](https://github.com/Vishal-raj-1/DSA-In-JS-With-Vishal/blob/main/String/README.md)
 - [Recursion](https://github.com/Vishal-raj-1/DSA-In-JS-With-Vishal/blob/main/Recursion/README.md)
-- [Linear & Binary Search](https://github.com/Vishal-raj-1/DSA-In-JS-With-Vishal/blob/main/Searching%20Algorthims/README.md)
+- [Linear & Binary Search](https://github.com/Vishal-raj-1/DSA-In-JS-With-Vishal/blob/main/Searching%20Algorthims/README.md)
+- [Objects](https://github.com/Vishal-raj-1/DSA-In-JS-With-Vishal/blob/main/Objects/README.md)
