diff --git a/index.html b/index.html
index 7445a44..7c8ad60 100644
--- a/index.html
+++ b/index.html
@@ -1,31 +1,38 @@
 <!DOCTYPE html>
 <html lang="en">
-<head>
-    <meta charset="UTF-8">
-    <meta http-equiv="X-UA-Compatible" content="IE=edge">
-    <meta name="viewport" content="width=device-width, initial-scale=1.0">
-    <title>Excel Sheet Generator</title>
-    <link rel="stylesheet" href="./style.css">
-    <link rel="preconnect" href="https://fonts.googleapis.com">
-    <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin>
-    <link href="https://fonts.googleapis.com/css2?family=Bitter:wght@500&display=swap" rel="stylesheet">
-</head>
-<body>
-    <div class="form">
-        <h1>Excel Sheet Generator</h1>
-        <input type="number" class="rows" placeholder="Enter number of rows">
-        <input type="number" class="columns" placeholder="Enter number of columns">
-        <div class="btns">
-            <button onclick="generateTable()">Generate</button>
-            <button onclick="ExportToExcel('xlsx')">Export</button>
+    <head>
+        <meta charset="UTF-8">
+        <meta http-equiv="X-UA-Compatible" content="IE=edge">
+        <meta name="viewport" content="width=device-width, initial-scale=1.0">
+        <title>Excel Sheet Generator</title>
+        <link rel="stylesheet" href="./style.css">
+        <link rel="preconnect" href="https://fonts.googleapis.com">
+        <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin>
+        <link
+            href="https://fonts.googleapis.com/css2?family=Bitter:wght@500&display=swap"
+            rel="stylesheet">
+    </head>
+    <body>
+        <div class="form">
+            <h1>Excel Sheet Generator</h1>
+            <input type="number" class="rows"
+                placeholder="Enter number of rows">
+            <input type="number" class="columns"
+                placeholder="Enter number of columns">
+            <div class="btns">
+                <button onclick="generateTable()">Generate</button>
+                <button onclick="ExportToExcel('xlsx')">Export</button>
+            </div>
         </div>
-    </div>
-    <div class="table">
-        <table cellspacing="6px">
-            <tbody class="sheet-body"></tbody>
-        </table>
-    </div>
-</body>
-<script type="text/javascript" src="https://unpkg.com/xlsx@0.15.1/dist/xlsx.full.min.js"></script>
-<script src="./script.js"></script>
+        <div class="table">
+            <table cellspacing="6px">
+                <tbody class="sheet-body"></tbody>
+            </table>
+        </div>
+    </body>
+    <script src="https://unpkg.com/sweetalert/dist/sweetalert.min.js"></script>
+
+    <script type="text/javascript"
+        src="https://unpkg.com/xlsx@0.15.1/dist/xlsx.full.min.js"></script>
+    <script src="./script.js"></script>
 </html>
\ No newline at end of file
diff --git a/script.js b/script.js
index bb93c4d..cc2dee6 100644
--- a/script.js
+++ b/script.js
@@ -1,29 +1,42 @@
+// swal("Hello world!");
+
 let table = document.getElementsByClassName("sheet-body")[0],
-rows = document.getElementsByClassName("rows")[0],
-columns = document.getElementsByClassName("columns")[0]
-tableExists = false
+  rows = document.getElementsByClassName("rows")[0],
+  columns = document.getElementsByClassName("columns")[0];
+tableExists = false;
 
 const generateTable = () => {
-    let rowsNumber = parseInt(rows.value), columnsNumber = parseInt(columns.value)
-    table.innerHTML = ""
-    for(let i=0; i<rowsNumber; i++){
-        var tableRow = ""
-        for(let j=0; j<columnsNumber; j++){
-            tableRow += `<td contenteditable></td>`
-        }
-        table.innerHTML += tableRow
-    }
-    if(rowsNumber>0 && columnsNumber>0){
-        tableExists = true
+  let rowsNumber = parseInt(rows.value),
+    columnsNumber = parseInt(columns.value);
+  console.log("start table");
+  // check if fields empty
+  if (!rowsNumber || !columnsNumber || rowsNumber < 0 || columnsNumber < 0) {
+    swal("fields must not be empty and greater than 0");
+    return;
+  }
+
+  //   render and generate table
+  table.innerHTML = "";
+  for (let i = 0; i < rowsNumber; i++) {
+    var tableRow = "";
+    for (let j = 0; j < columnsNumber; j++) {
+      tableRow += `<td contenteditable></td>`;
     }
-}
+    table.innerHTML += tableRow;
+  }
+  if (rowsNumber > 0 && columnsNumber > 0) {
+    tableExists = true;
+  }
+};
 
 const ExportToExcel = (type, fn, dl) => {
-    if(!tableExists){
-        return
-    }
-    var elt = table
-    var wb = XLSX.utils.table_to_book(elt, { sheet: "sheet1" })
-    return dl ? XLSX.write(wb, { bookType: type, bookSST: true, type: 'base64' })
-        : XLSX.writeFile(wb, fn || ('MyNewSheet.' + (type || 'xlsx')))
-}
\ No newline at end of file
+  if (!tableExists) {
+    swal("table not exists");
+    return;
+  }
+  var elt = table;
+  var wb = XLSX.utils.table_to_book(elt, { sheet: "sheet1" });
+  return dl
+    ? XLSX.write(wb, { bookType: type, bookSST: true, type: "base64" })
+    : XLSX.writeFile(wb, fn || "MyNewSheet." + (type || "xlsx"));
+};
