Completed some JS algorithms (#35)

* Added merge sort in JS

* Added bubble sort code

* added heap sort code

* added selection sort code

Javascript/binarysearch.js

@@ -1,7 +1,23 @@
 // Binary Search Algorithm in Javascript
 
 function binarySearch(arr, x) {
-    // your code here
+    let start=0, end=arr.length-1;
+
+
+    while (start<=end){
+
+        let mid=Math.floor((start + end)/2);
+
+
+        if (arr[mid]===x) return true;
+
+        else if (arr[mid] < x)
+             start = mid + 1;
+        else
+             end = mid - 1;
+    }
+
+    return false;
 }
 
 var arr = [2, 3, 4, 10, 40];
@@ -13,4 +29,4 @@ var result = binarySearch(arr, x);
 console.log(result);
 
 // Output:
-// 3
+// true

Javascript/bubblesort.js

@@ -1,7 +1,14 @@
 // Bubble Sort in JavaScript
 
 function bubbleSort(arr) {
-    // your code here
+    for (let i = arr.length - 1; i > 0; i--) {
+        for (let j = 0; j < i; j++) {
+          if (arr[j] > arr[j + 1]) {
+            [arr[j], arr[j + 1]] = [arr[j + 1], arr[j]]
+          }
+        }
+      }
+      return arr
 }
 
 var arr = [76, 22, 21, 96, 70, 20];

Javascript/checkprime.js

@@ -1,8 +1,11 @@
 // Check if a number is prime or not using JavaScript
 
 function isPrime(num) {
-    // your code here
-    // return true or false
+    for(var i = 2 ; i<=num/2 ; i++){
+        if(num%i == 0)return false;
+    }
+
+    return true;
 }
 
 console.log(isPrime(73)); 

Javascript/fibonacci.js

@@ -1,7 +1,7 @@
 // Fibonacci sequence generator in JavaScript 
 
 function fibonacci(n) {
-    // your code here
+
 }
 
 console.log(fibonacci(10));

Javascript/heapsort.js

@@ -1,7 +1,43 @@
 // Heap Sort in JavaScript
 
+const maxHeapify = (arr, n, i) => {
+    let largest = i;
+    let l = 2 * i + 1;
+    let r = 2 * i + 2; 
+
+     if (l < n && arr[l] > arr[largest]) {
+           largest = l; 
+     }
+
+     if (r < n && arr[r] > arr[largest]) {
+          largest = r; 
+     }
+
+
+     if (largest != i) { 
+          let temp = arr[i]; 
+          arr[i] = arr[largest]; 
+          arr[largest] = temp; 
+
+        maxHeapify(arr, n, largest); 
+      } 
+  }
+
+
 function heapSort(arr) {
-    // your code here
+     var n = arr.length;
+      for (let i = parseInt(n / 2 - 1); i >= 0; i--) {
+        maxHeapify(arr, n, i); 
+    }
+
+    for (let i = n - 1; i >= 0; i--) { 
+       let temp = arr[0]; 
+       arr[0] = arr[i]; 
+       arr[i] = temp;  
+       maxHeapify(arr, i, 0); 
+    } 
+
+    return arr;
 }
 
 var arr = [76, 22, 21, 96, 70, 20];

Javascript/mergesort.js

@@ -0,0 +1,61 @@
+// Merge Sort Algorithm in Javascript 
+
+function mergeSortRec(arr){
+
+    const length = arr.length;
+
+    if(length === 1){
+      return arr;
+    }
+
+    const mid = Math.floor(length / 2);
+
+    const left = arr.slice(0, mid);
+
+    const right = arr.slice(mid, length);
+
+    return merge(mergeSortRec(left), mergeSortRec(right));
+  }
+
+  function merge(leftArr, rightArr){
+
+    const result = [];
+
+    let iL = 0; 
+    let iR = 0; 
+
+
+    while(iL < leftArr.length && iR < rightArr.length){
+      if(leftArr[iL] < rightArr[iR]){
+        result.push(leftArr[iL]);
+        iL++;
+      }else{
+        result.push(rightArr[iR]);
+        iR++;
+      }
+    }
+
+
+    while(iL < leftArr.length){
+      result.push(leftArr[iL]);
+      iL++;
+    }
+
+
+    while(iR < rightArr.length){
+      result.push(rightArr[iR]);
+      iR++;
+    }
+
+    return result;
+  }
+
+var arr = [3, 2, 10, 140, 5, 0 , 100, 38];
+var result = mergeSortRec(arr);
+console.log(result);
+
+// Output
+// [
+//     0,  2,   3,   5,
+//    10, 38, 100, 140
+//  ]

Javascript/selectionsort.js

@@ -1,12 +1,24 @@
 // Selection Sort in JavaScript 
 
 function selectionSort(arr) {
-    // your code here
+    for (var i = 0; i < arr.length; i++) {  
+        var temp = arr[i];  
+        for (var j = i + 1; j < arr.length; j++) {  
+            if (temp > arr[j]) {  
+                temp = arr[j];  
+            }  
+        }  
+        var index = arr.indexOf(temp);  
+        var tempVal = arr[i];  
+        arr[i] = temp;  
+        arr[index] = tempVal;  
+    }  
 }
 
 var arr = [76, 22, 21, 96, 70, 20];
 
-console.log(selectionSort(arr));
+selectionSort(arr);
+console.log(arr);
 
 // Output: