Javascript script to check if number is triangle number.
// ? 2017 TheFlyingKeyboard and released under MIT License // theflyingkeyboard.net <html> <body> Enter a number: <input type="text" id="data"> <button onclick="check()">Convert</button> <p id="newText"></p> <script> function check(){ var data = document.getElementById("data").value; var n = parseInt(data); if(isSquare(8 * n + 1)){ document.getElementById("newText").innerHTML = "Number is triangle number"; } else { document.getElementById("newText").innerHTML = "Number is not triangle number"; } } function isSquare(n) { for (var i = 0; i < n / 2 + 2; i++) { if (i * i == n) { return true; } } return false; } </script> </body> </html>