added array methods

Author: ummeabiha

Array.js

@@ -2,34 +2,34 @@
 // Array is an object (non-primitive)
 // Array are mutable which can be directly accessed and changed
 
-let marks= [90, 70, 85, 24];
+let marks = [90, 70, 85, 24];
 console.log(marks);
 console.log(marks.length); //property not a method
 
-//**************************************************************************************/ 
+//**************************************************************************************/
 // Looping Over Arrays
 
 // For Loop
-for (let i=0; i<marks.length; i++){
-    console.log(marks[i]);
+for (let i = 0; i < marks.length; i++) {
+  console.log(marks[i]);
 }
 
 // For Of Loop
 for (let i of marks) {
-    console.log(i);
+  console.log(i);
 }
 
-//**************************************************************************************/ 
+//**************************************************************************************/
 // Array Methods
-let foodItems= ["Potato", "Apple", "Strawberry", "Tomato"];
-let drinks= ["Coca Cola", "Pakola", "7UP", "Sprite"];
+let foodItems = ["Potato", "Apple", "Strawberry", "Tomato"];
+let drinks = ["Coca Cola", "Pakola", "7UP", "Sprite"];
 
 //Push() adds the item at the end of an original array
 foodItems.push("Chips", "Burgers");
 console.log(foodItems);
 
 // Pop() removes the item from the end of an original array & returns it
-let deleted= foodItems.pop();
+let deleted = foodItems.pop();
 console.log(`Deleted Item ${deleted}`);
 console.log(foodItems);
 
@@ -43,16 +43,16 @@ console.log(foodItems.concat(drinks));
 foodItems.unshift("Pasta");
 
 // Shift() Removes Item from the start of an array & returns
-let sDel= foodItems.shift();
+let sDel = foodItems.shift();
 console.log(sDel);
 
 // Slice() Returns a piece of the array slice(startidx, endidx)
-console.log(foodItems.slice(1,3));
+console.log(foodItems.slice(1, 3));
 
 // Splice() Change original array (add, remove, replace) splice(startidx, delCount, newEl1)
 // 2nd index sy start krky 3 elements delete krny hain and us 2nd index pai "jam" insert krna hai
 console.log("\n", foodItems);
-foodItems.splice(2,3,"jam");
+foodItems.splice(2, 3, "jam");
 console.log("\n", foodItems);
 
 // Add Element
@@ -65,4 +65,94 @@ console.log("\n", foodItems);
 
 // Replace Element
 foodItems.splice(1, 1, "cookie");
-console.log("\n", foodItems);
+console.log("\n", foodItems);
+
+//**************************************************************************************/
+//WHAT ARE HIGHER ORDER FUNCTIONS / METHODS (HOD/HOM) ????????????//
+/*
+HOD takes functions either as parameters or returns a function as a value
+Such as: forEach is a HOD function
+*/
+
+//**************************************************************************************/
+//ForEach Loop in Arrays
+
+let arr = [1, 2, 3, 4, 5, 6, 7, 8];
+
+//forEach will take each array element as a value here.
+//forEach automatically executes the function, we do not need to do it.
+arr.forEach(function printValue(val) {
+  console.log(val);
+});
+
+let cities = ["Lahore", "Faisalabad", "Karachi", "Hyderabad"];
+cities.forEach((val) => {
+  console.log(val.toUpperCase());
+});
+
+/*FOR EACH CAN TAKE 3 PARAMATERS i.e. value, index, and array (optional)*/
+cities.forEach((val, idx, arr) => {
+  console.log(val.toUpperCase(), idx, arr);
+});
+
+//**************************************************************************************/
+// MAP in Arrays
+// Map and ForEach are very similar to each other. They both are utilized to access each element of an array. The only difference is map returns a new array, but forEach() does not.
+// forEach() is used to perform simple calculations, while map() is used when we need a new array with some specific operation performed on it.
+
+arr.map((val) => {
+  console.log(val);
+});
+
+let calSq = arr.map((val) => {
+  return val * val;
+});
+
+console.log(calSq);
+
+//**************************************************************************************/
+/* FILTER METHOD
+Creates a new array of values that give true for a specified condition or filter
+*/
+let even = arr.filter((val) => {
+  return val % 2 == 0;
+});
+console.log(even);
+
+let odd = arr.filter((val) => {
+  return val % 2 !== 0;
+});
+console.log(odd);
+
+//**************************************************************************************/
+/* REDUCE METHOD
+Performs some operations and reduce the array to a single. It return that single value.
+
+It works like this:
+for suppose let arr= [1,2,3,4]
+const output= arr.reduce((res, curr)=>{
+    return res+curr;
+});
+
+1st iteration
+res=1, curr= 2 ---> after execution res=3
+2nd iteration
+res= 3, curr= 3 ---> after execution res=6
+3rd iteration
+res= 6, curr= 4 ---> after execution res=10
+
+Output will be 10
+*/
+
+const output = arr.reduce((res, curr) => {
+  return res + curr;
+});
+
+console.log(output);
+
+// Find the largest element in the array
+const largest = arr.reduce((prev, curr) => {
+  return prev > curr ? prev : curr;
+});
+
+console.log(largest);