Add jumpSearch algorithm

src/_Searching_/JumpSearch/JumpSearch.test.js

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+const { jumpSearch, jumpSearchRecursive } = require('.');
+
+describe('Jump Search', () => {
+    const array = [1, 2, 3, 4, 5, 6, 7, 8];
+    const jump = 3;
+    describe('When element to find is at 1st position ', () => {
+        it('Jump search', () => {
+          expect(jumpSearch(array, jump, 1)).toEqual(0);
+        });
+      });
+    describe('When element to find is at last position ', () => {
+        it('Jump search', () => {
+          expect(jumpSearch(array, jump, 7)).toEqual(6);
+        });
+      });
+    describe('When element to find is at random position ', () => {
+        it('Jump search', () => {
+          expect(jumpSearch(array, jump, 3)).toEqual(2);
+        });
+      });
+    describe('When jump is larger than array', () => {
+        it('Jump search', () => {
+          expect(jumpSearch(array, 9, 3)).toEqual(2);
+        });
+      });
+});

src/_Searching_/JumpSearch/index.js

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+function jumpSearch(arr, jump, key) {
+    // treat jumps larger than array size as linear search
+    jump = jump > arr.length ? 1 : jump;
+
+    let low = 0, high = 0;
+    for (let i = jump; i < arr.length; i+=jump) {
+        if(key < arr[i]) {
+            high = i;
+            low = i - jump;
+            break;
+        }
+    }
+
+    // check if loop has finished without finding key
+    if(high == 0) {
+        high = arr.length;
+        low = high - jump;
+    }
+
+    for(let i = low; i < high; i++) {
+        if(arr[i] == key) {
+            // return the index of the key
+            return i;
+        }
+    }
+    return null;
+  }
+
+  module.exports = {
+    jumpSearch,
+  };