added some files

Author: AnuragAnalog

README.md

@@ -184,7 +184,7 @@ console.log(a % b); // prints 10 to the console
 There is also a shorthand notation of the operations, which is used to perform operations on the same variable.
 
 ```javascript
-var a = 10;
+let a = 10;
 a += 10; // a = a + 10
 console.log(a); // prints 20 to the console
 // Similarly, there are other operations like -=, *=, /=, %=
@@ -226,13 +226,13 @@ arr[2] = 10;
 console.log(arr); // prints [undefined, undefined, 10] to the console
 ```
 
-If a empty array is defined, then the array is filled with `undefined` values.
+If an empty array is defined, then the array is filled with `undefined` values.
 
 This datatype also has some special properties, we can also apply stack and queue operations on it.
 
 **Stack Operations**
 ```javascript
-var arr = [1, 2, 3, 4, 5];
+let arr = [1, 2, 3, 4, 5];
 arr.push(6); // push operation
 console.log(arr); // prints [1, 2, 3, 4, 5, 6] to the console
 arr.pop(); // pop operation
@@ -244,30 +244,58 @@ When running a push operation, it will return the length of the array.
 
 **Queue Operations**
 ```javascript
-var arr = [1, 2, 3, 4, 5];
+let arr = [1, 2, 3, 4, 5];
 console.log(arr.shift()); // dequeue operation (prints 1 to the console)
 arr.unshift(6); // enqueue operation(to the first index)
 console.log(arr); // prints [6, 2, 3, 4, 5] to the console
 ```
 
 **Slicing an Array**
 ```javascript
-var arr = [1, 2, 3, 4, 5, 6, 7, 8, 9];
-var slice = arr.slice(2, 5); // slice(start_index, count)
+let arr = [1, 2, 3, 4, 5, 6, 7, 8, 9];
+let slice = arr.slice(2, 5); // slice(start_index, count)
 console.log(slice); // prints [3, 4, 5, 6, 7] to the console
 console.log(arr); // prints [1, 2, 8, 9]
 ```
 
 To apply a specific operation on each element of the array, we can use the `forEach()` method.
 
 ```javascript
-var arr = [1, 2, 3, 4, 5];
+let arr = [1, 2, 3, 4, 5];
 
 arr.forEach((element) => {
     console.log(element);
 });
 ```
 
+Filtering on the array can be done, using the `filter()` method. It will return a new array, which contains the elements which satisfy the condition.
+
+```javascript
+let arr = [11, 25, 13, 42, 54, 6, 78];
+
+let filtered = arr.filter((element) => {
+    return element > 25;
+});
+console.log(filtered); // prints [42, 54, 78] to the console
+// Here you can see that only elements greater than 25 are returned
+```
+
+The next method, which we are going to learn is the find method. It will return the first element which satisfies the condition. If no element is matched then, it will return `undefined`.
+
+```javascript
+let arr = [11, 25, 13, 42, 54, 6, 78];
+
+let filtered = arr.find((element) => {
+    return element > 25;
+});
+console.log(filtered); // prints 42 to the console
+```
+
+The main, difference between the `filter()` and `find`() methods is the return datatype of the methods, `filter()` returns an array, whereas `find()` returns the element.
+
+* Filter will always return an array, even if there is only one element or no element in the array.
+* Find will return the element, if there is only one element in the array, otherwise it will return undefined.
+
 ## Conditions
 
 Conditions are used to check whether a condition is true or false, and based on that we can perform some operations.

print.js

@@ -0,0 +1 @@
+console.log("Hello World");

variables.js

@@ -0,0 +1,49 @@
+const integer = 10; // Integer variable
+const string = "Hello World"; // String variable
+const float = 10.5; // Float variable
+const boolean = true; // Boolean variable
+
+const arr = [1, 2, 3, 4, 5]; // Array variable
+const obj = { name: "John", age: 20 }; // Object variable (similar to dict in python)
+
+let nd_var;
+console.log(nd_var); // prints undefined to the console
+
+const null_var = null;
+console.log(null_var);
+
+const const_var = 10;
+let let_var = 10;
+
+const_var = 20; // throws an error in the JavaScript
+let_var = 20; // works fine
+
+const str = "Hello World";
+console.log(str.length); // prints 11 to the console
+console.log(str.toUpperCase()); // prints HELLO WORLD to the console
+console.log(str.toLowerCase()); // prints hello world to the console
+
+const str = "Hello World";
+console.log(str[0]); // prints H to the console
+console.log(str.at(0)); // prints H to the console
+console.log(str.at(-1)); // prints d to the console
+
+const str = "Hello World";
+console.log(str.substring(0, 5)); // prints Hello to the console
+console.log(str.substring(6)); // prints World to the console
+
+const name = "John";
+console.log(`Hello ${name}`); // prints Hello John to the console
+
+const num = 10000;
+console.log(num.toString()); // prints 10000 to the console
+
+const num = 100_000_000;
+// is same as 100000000
+
+const str = "100";
+console.log(Number.parseInt(str, 10)); // 100, the second argument is the base of the number
+
+const str = "100px";
+console.log(Number.parseInt(str, 10)); // 100
+// It ignores the px at the end