<body> <h1>Adding 'a' and 'b'</h1> a: <input type="number" name="a" id="a"><br> b: <input type="number" name="b" id="b"><br> <button onclick="add(document.getElementById('a').value,document.getElementById('b').value)">Add</button> <script> function add(a, b) { var sum = parseInt(a, 10) + parseInt(b, 10); alert(sum); } </script> </body> OTRO EJEMPLO <script> function eq(value) { console.log(value); ViewImg = window.open('http://localhost/coord.php?' + value, 'ViewImg', 'width=<?php print $realWidthNewWindow; ?>,height=<?php print $realHeightNewWindow; ?>', 'status=no', 'titlebar=0'); } </script> <form id='testform_eq' name='testform_new'> <input type='text' id='val2' name='val2'> <input type='button' value='Submit' onclick='eq(document.getElementById("val2").value)'> </form> OTRO EJEMPLO <body> <h1>Adding 'a' and 'b'</h1> <form> a: <input type="number" name="a" id="a"><br> b: <input type="number" name="b" id="a"><br> <button onclick="add()">Add</button> </form> <script> function add() { var m = document.getElementById("a").value; var n = document.getElementById("b").value; var sum = m + n; alert(sum); Var sum = parseFloat(a)+parseFloat (b); } </script> </body>