map.filter and reduce

Author: swathireddy369

MapFilterReduce.js

@@ -0,0 +1,65 @@
+let arr = [5, 1, 3, 6, 2];
+
+// function double(i){
+//      return i*2;
+// }
+// function triple(i){
+//      return i*3;
+// }
+// function binary(i){
+//      return i.toString(2);//to convert number into binary
+// }
+// let output=arr.map(double);
+console.log(arr.map(function double(i) { ///1way
+     return i * 2;
+}));
+console.log(arr.map(function (i) {
+     return i * 3;
+}));
+console.log(arr.map((i) => i.toString(2)));//finak efficinet way of writting map
+
+
+console.log("=============================filter===========================");
+function isOdd(i) {
+     return i % 2;
+}
+function isEven(i) {
+     return i % 2;
+}
+let output = arr.filter(isOdd);
+console.log(arr.filter(function isOdd(i) {
+     return i % 2;//odd
+}));
+console.log(arr.filter((i) => {
+     return i % 2 == 0;//even
+}));
+console.log(arr.filter((i) => i % 2 !== 0));//not even
+
+console.log("========================reduce===========================");
+function sum(acc, curr) {
+     acc += curr;
+     return acc;
+}
+
+console.log(arr.reduce(sum, 0));
+console.log(arr.reduce(function sum(acc, curr) {
+     acc += curr;
+     return acc;
+}, 0));
+console.log(arr.reduce(function max(acc, curr) {
+     if (acc < curr) {
+          acc = curr;
+     }
+     return acc;
+
+}, 0));
+console.log(arr.reduce((acc, curr)=> {
+     if (acc < curr) {
+          acc = curr;
+     }
+     return acc;
+
+}, 0));
+
+
+

MapFilterReducev2.js

@@ -0,0 +1,36 @@
+let arr = [{first: "Swathi", lastName: "Amaravadi", age: "27"},
+{ first: "Rajesh", lastName: "kodakandla", age: "33" },
+{ first: "gopireddy", lastName: "Amaravadi", age: "25" },
+{ first: "Anand", lastName: "yannamaneni", age: "27" }]
+
+// [{"swathi Amaravadi"}]
+// as we need to get transformation of input for all input objects so in that case should use Map
+
+let output1 = arr.map((x) => x.first + " " + x.lastName);
+console.log(output1);
+
+
+//here we need to get a output of object that contains all age entries in the array and frequencyies of it so as we are not transforming input array and not filtering from that juist forming new output from given input
+
+let output2 = arr.reduce((acc, curr) => {
+    if (acc[curr.age]) {
+        acc[curr.age]++;
+    } else {
+        acc[curr.age] = 1;
+    }
+    return acc;
+}, {});
+console.log(output2);
+
+//here need to get only lastnames of whose age is greater than 30
+let output3 = arr.filter((x) => x.age > 30).map((x) => x.lastName);
+console.log(output3);
+
+
+let output = arr.reduce(function (acc, curr) {
+    if (curr.age > 30) {
+        acc.push(curr.lastName);
+    }
+    return acc;
+}, [])
+console.log(output);

README.md

@@ -791,4 +791,126 @@ https://claude.ai/public/artifacts/29027752-4a20-451f-a5a0-743050848a4b
 3.call back function a function that passed trhough argument fir another function
 
 
-here call back function passed as argument to huigher order function its abiloity is called first class function
+here call back function passed as argument to huigher order function its abiloity is called first class function
+
+
+Day-8:
+
+// Sample array
+let arr = [5, 1, 3, 6, 2];
+
+// ========================== MAP ==========================
+console.log("================= MAP =================");
+// MAP: Creates a new array by applying a function to each element
+
+// Method 1: Named function declaration outside map
+function double(i) {
+    return i * 2;
+}
+console.log("Double:", arr.map(double));
+
+// Method 2: Anonymous function inside map
+console.log("Triple:", arr.map(function(i) {
+    return i * 3;
+}));
+
+// Method 3: Arrow function (most concise)
+console.log("Binary:", arr.map(i => i.toString(2)));
+
+
+// ========================== FILTER ==========================
+console.log("\n================= FILTER =================");
+// FILTER: Creates a new array with elements that pass a test
+
+// Method 1: Named function declaration
+function isOdd(i) {
+    return i % 2; // Non-zero values are truthy (odd numbers)
+}
+console.log("Odd numbers:", arr.filter(isOdd));
+
+// Method 2: Anonymous function
+console.log("Even numbers:", arr.filter(function(i) {
+    return i % 2 === 0;
+}));
+
+// Method 3: Arrow function
+console.log("Odd numbers (arrow):", arr.filter(i => i % 2 !== 0));
+
+
+// ========================== REDUCE ==========================
+console.log("\n================= REDUCE =================");
+// REDUCE: Accumulates array values into a single result
+
+// Method 1: Named function declaration
+function sum(acc, curr) {
+    acc += curr;
+    return acc;
+}
+console.log("Sum:", arr.reduce(sum, 0));
+
+// Method 2: Anonymous function
+console.log("Sum (anonymous):", arr.reduce(function(acc, curr) {
+    acc += curr;
+    return acc;
+}, 0));
+
+// Method 3: Finding maximum value
+console.log("Max value:", arr.reduce(function(acc, curr) {
+    if (acc < curr) {
+        acc = curr;
+    }
+    return acc;
+}, 0));
+
+// Method 4: Max with arrow function
+console.log("Max (arrow):", arr.reduce((acc, curr) => {
+    if (acc < curr) {
+        acc = curr;
+    }
+    return acc;
+}, 0));
+
+
+// ========================== PRACTICAL EXAMPLES ==========================
+console.log("\n================= PRACTICAL EXAMPLES =================");
+
+// Array of objects
+let people = [
+    {first: "Swathi", lastName: "Amaravadi", age: "27"}, 
+    {first: "Rajesh", lastName: "Kodakandla", age: "33"}, 
+    {first: "Gopireddy", lastName: "Amaravadi", age: "25"}, 
+    {first: "Anand", lastName: "Yannamaneni", age: "27"}
+];
+
+// Example 1: Map - Create full names array
+let fullNames = people.map(person => person.first + " " + person.lastName);
+console.log("Full names:", fullNames);
+
+// Example 2: Reduce - Count occurrences of each age
+let ageFrequency = people.reduce((acc, curr) => {
+    if (acc[curr.age]) {
+        acc[curr.age]++;
+    } else {
+        acc[curr.age] = 1;
+    }
+    return acc;
+}, {});
+console.log("Age frequency:", ageFrequency);
+
+// Example 3: Chaining methods - Get lastNames of people over 30
+let over30LastNames = people
+    .filter(person => person.age > 30)
+    .map(person => person.lastName);
+console.log("LastNames of people over 30:", over30LastNames);
+
+// Example 4: Alternative using reduce for the same operation
+let over30LastNamesAlt = people.reduce((acc, curr) => {
+    if (curr.age > 30) {
+        acc.push(curr.lastName);
+    }
+    return acc;
+}, []);
+console.log("LastNames of people over 30 (with reduce):", over30LastNamesAlt);
+
+
+https://claude.ai/public/artifacts/864c8182-bd9e-4d29-827a-2e21653dbf10

index.html

@@ -1,6 +1,6 @@
 <!DOCTYPE html>
 <html>
     <head>
-    <script src="./LeetCode-counter-ii"></script>
+    <script src="./MapFilterReducev2.js"></script>
 </head>
 </html>