add sort to higher_order_functions under JS Basics_Info

docs/JavaScript_Basics/Datatypes.md

@@ -1,12 +1,13 @@
 ```js
 var length = 16; // Number
-var bigLength = BigInt(16) // BigInt
-var lastName = "Johnson"; // String
-var x = { firstName: "John", lastName: "Doe" }; // Object
+var bigLength = BigInt(16); // BigInt
+var lastName = 'Johnson'; // String
+var x = { firstName: 'John', lastName: 'Doe' }; // Object
 var nullValue = null; // null
 var undefinedValue = undefined; // undefined
 var booleanValue = true; // Boolean
 var newSymbol = Symbol("I'm new in es6!"); // Symbol
+var notNumber = NaN; // Number
 
 // the type of every variable in javascript can be checked using typeof(var)
-```
+```

docs/JavaScript_Basics_Info/higher_order_functions.md

@@ -3,91 +3,123 @@
 A **Higher Order function** or **HOF** is a function that receives a function as an argument or returns the function as output.
 
 There are some built-in HOF for Arrays in Javascript, such as
-  - *Array.prototype.map*
-  - *Array.prototype.filter*
-  - *Array.prototype.reduce*.
+
+- _Array.prototype.map_
+- _Array.prototype.filter_
+- _Array.prototype.reduce_.
 
 Let's understand each of these through examples.
 
 We will use the below array `list` as the base array to operate over.
 
 ```js
-  const list = [1, 2, 3, 4, 5];
+const list = [1, 2, 3, 4, 5];
 ```
 
 ## 1. map
 
- - The **map** function iterates over an input array and returns a new array.
- - It does not change the original array, but creates a new array.
- - The map receives a callback function as its argument. This callback function receives 3 arguments
-    - 1st arg is the **elememt** of the array, like 1, 2, 3, 4, 5
-    - 2nd arg is the **index** of the item in the list (index for first element is 0, and so on)
-    - 3rd arg is the original array [1,2,3,4,5] on which map is being called
+- The **map** function iterates over an input array and returns a new array.
+- It does not change the original array, but creates a new array.
+- The map receives a callback function as its argument. This callback function receives 3 arguments
+  - 1st arg is the **elememt** of the array, like 1, 2, 3, 4, 5
+  - 2nd arg is the **index** of the item in the list (index for first element is 0, and so on)
+  - 3rd arg is the original array [1,2,3,4,5] on which map is being called
 
 ```js
-  const newList = list.map(function (item, index, list) {
-    return item * 2;
-  });
+const newList = list.map(function (item, index, list) {
+	return item * 2;
+});
 
-  console.log(list);        // prints [1, 2, 3, 4, 5]
-  console.log(newList);     // prints [2, 4, 6, 8, 10]
+console.log(list); // prints [1, 2, 3, 4, 5]
+console.log(newList); // prints [2, 4, 6, 8, 10]
 ```
 
-
 ## 2. filter
 
-  - the **filter** function iterates over an input array and returns a new array based on a condition
-  - the filter receive a callnack function as its argument. This callback functions receives 3 arguments:
-    - 1st arg is the **element** in the list like "1" or "2" in the list example
-    - 2nd arg is the **index** of the item in the list (index for first element is 0, and so on)
-    - 3rd arg is the original array [1,2,3,4,5] on which filter is being called
+- the **filter** function iterates over an input array and returns a new array based on a condition
+- the filter receive a callnack function as its argument. This callback functions receives 3 arguments:
+  - 1st arg is the **element** in the list like "1" or "2" in the list example
+  - 2nd arg is the **index** of the item in the list (index for first element is 0, and so on)
+  - 3rd arg is the original array [1,2,3,4,5] on which filter is being called
 
-  ```js
-  // this filtered list will contain only even numbers
+```js
+// this filtered list will contain only even numbers
 
-  const newListFiltered = list.filter(function (item, index, list) {
-    // filter will return the value if it satisfies the below condition
-    return item % 2 === 0;
-  });
+const newListFiltered = list.filter(function (item, index, list) {
+	// filter will return the value if it satisfies the below condition
+	return item % 2 === 0;
+});
 
-  console.log(list);        // prints [1, 2, 3, 4, 5]
-  console.log(newList);     // prints [2, 4]
-  ```
+console.log(list); // prints [1, 2, 3, 4, 5]
+console.log(newList); // prints [2, 4]
+```
 
 ## 3. reduce
 
-  - the **reduce** function iterates over an input array and returns a single output value
-  - it receives two arguments:
-    - a callback function, also called as **reducer** function
-    - an **initialValue** (this is optional parameter)
-  - the reducer function accepts four parameters:
-    - 1st arg is **accumulator** which contains the accumulated value which will be returned when the array is reduced.
-      If initalvalue is provided, accumulator will be equal to initialvalue, else it will be equal to the first element in the array
-    - 2nd arg is **currentValue** which points to the current value of the array which is being iterated over.
-      If initalvalue is provided, currentValue will be equal to the first element in the array, else it will be equal to the second element in the array
-    - 3rd arg is **index** which contains the index of the currentValue in the input array
-    - 4th arg is the **sourceArray** which is the input array on which reduce is called
+- the **reduce** function iterates over an input array and returns a single output value
+- it receives two arguments:
+  - a callback function, also called as **reducer** function
+  - an **initialValue** (this is optional parameter)
+- the reducer function accepts four parameters:
+  - 1st arg is **accumulator** which contains the accumulated value which will be returned when the array is reduced.
+    If initalvalue is provided, accumulator will be equal to initialvalue, else it will be equal to the first element in the array
+  - 2nd arg is **currentValue** which points to the current value of the array which is being iterated over.
+    If initalvalue is provided, currentValue will be equal to the first element in the array, else it will be equal to the second element in the array
+  - 3rd arg is **index** which contains the index of the currentValue in the input array
+  - 4th arg is the **sourceArray** which is the input array on which reduce is called
 
 ```js
 // Example 1
 // this will return sum of all items in list. here, there is no initialvalue provided
 
-const sumOfListItems = list.reduce(function(accumulator, currentValue) {
-  return accumulator + currentValue;
+const sumOfListItems = list.reduce(function (accumulator, currentValue) {
+	return accumulator + currentValue;
 });
 
-console.log(list);            // prints [1, 2, 3, 4, 5]
-console.log(sumOfListItems);  // prints 15
+console.log(list); // prints [1, 2, 3, 4, 5]
+console.log(sumOfListItems); // prints 15
 ```
 
 ```js
 // Example 2
 // this will return sum of all items in list. here, the initialvalue is provided as 20
 
-const newSumOfListItems = list.reduce(function(accumulator, currentValue) {
-  return accumulator + currentValue;
+const newSumOfListItems = list.reduce(function (accumulator, currentValue) {
+	return accumulator + currentValue;
 }, 20);
 
-console.log(list);            // prints [1, 2, 3, 4, 5]
-console.log(newSumOfListItems);  // prints 35 (the sum of list items is 15, and the initial value was 20, so, 20 + 15 = 35)
+console.log(list); // prints [1, 2, 3, 4, 5]
+console.log(newSumOfListItems); // prints 35 (the sum of list items is 15, and the initial value was 20, so, 20 + 15 = 35)
+```
+
+## 4. sort
+
+- If no input function is provided, values are sorted as strings by default, which means even if the elements are numbers, it converts them to strings and compare them with alphabetic order.
+- To sort numbers, a compare function is needed. The compare function takes two arguments (a, b).
+- Ascending oder: If the return (a-b) is negative, a comes before b. If the return (a-b) is positive, a comes after b.
+- Descending oder: If the return (b-a) is negative, a comes before b. If the return (b-a) is positive, a comes after b.
+
+```js
+// Example 1
+const fruits = ['apple', 'orange', 'grape'];
+console.log(fruits.sort()); // prints ["apple","grape","orange"]
+```
+
+```js
+// Example 2
+const numList = [34, 67, 100, 20];
+console.log(numList.sort()); // prints [100,20,34,67]
+```
+
+```js
+// Example 3
+const numList = [34, 67, 100, 20];
+console.log(numList.sort()); // prints [100,20,34,67]
+```
+
+```js
+// Example 4
+const numList = [34, 67, 100, 20];
+console.log(numList.sort((a, b) => a - b)); // prints [20,34,67,100]
+console.log(numList.sort((a, b) => b - a)); // prints [100,67,34,20]
 ```