Added JavaScript implementation of quadratic probing in hashing.

data structures/javascript/quadraticHashing.js

@@ -0,0 +1,44 @@
+function hashFunction(input, hashTable) {
+    let index = input % hashTable.length;                          //index is assigned based on the hash-function on the RHS
+
+    let i = 1;
+    while (hashTable[index] !== null) {                            //if the array index is not null, i.e. occupied by other elements, the loop runs
+        index = (index + i ** 2) % hashTable.length;               //new index is assigned based on quadratic probing.(old index plus i squared)
+        i++;                                                       //% operation is used, incase the quadratic function gives a value out of bounds of the array
+    }
+    hashTable[index] = input;
+}
+
+function main() {
+    let tableSize = 10;                                           //setting table size 
+    let hashTable = Array(tableSize).fill(null);                  //initializing array and filling it with null
+    let choice = "Y";
+    while (choice == "Y") {
+
+        if (!(hashTable.includes(null))) {                        //if hash table is full, the loop ends and program terminates
+            alert("Table is full. PLease reset table size and re-enter the values.");
+            break;
+        }
+
+        let input = prompt("Enter number to enter into hash table:");
+        hashFunction(input, hashTable);
+
+        console.log("Hash Table Indices:");                       //The hash table is printed out onto the log.
+        let i = 0;
+        while (i < tableSize) {
+            console.log(i + ' ');
+            i++;
+        }
+
+        i = 0;
+        console.log("Hash Table Values:");
+        while (i < tableSize) {
+            console.log(hashTable[i] + ' ');
+            i++;
+        }
+
+        choice = prompt("Do you want to continue?(Y/N)")
+    }
+}
+//Contributed by Senthil Adithya github: a-dithya04
+main();