Why my code is not running ? Please help me ASAP.
<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>Calculator</title> <script> function history() { return document.getElementById("history-value").innerText=num; } function history(){ return document.getElementById("history-value").innerText=num; } function history(num){ document.getElementById("history-value").innerText=num; } function output() { return document.getElementById("output-value").innerText=num; } function output(num){ document.getElementById("output-value").innerText=getFormattedNumber(num); } output("9999"); </script> <style> body{ font-family:helvetica; background:#FFFFE0; } h1{ text-align:center; color:#008080; } #calculator{ background-color:#708090; width:320px; height:520px; margin: 0 auto; border-radius:5px; box-shadow:10px 10px, 10px 10px #888888; position:relative; top:20px; } #result{ height:120px; } #history{ text-align: right; height:20px; margin:0 20px; padding-top:20px; font-size:20px; color:#FDF5E6; } #output{ text-align: right; height:60px; margin:10px 20px; font-size:35px; font-weight: bold; } #keyboard{ height:400px; } .operator, .number, .empty{ width:50px; height:50px; margin:15px; float:left; border-radius:50%; border-width:0; font-weight:bold; font-size:15px; } .number, .empty{ background-color:#708090; } .number, .operator{ cursor: pointer; } .operator:active, .number:active{ font-size: 15px; } .operator:focus, .number:focus, .empty:focus{ outline: 0; } button:nth-child(4){ font-size: 20px; background-color: #87CEFA; } button:nth-child(8){ font-size: 20px; background-color: #00FF00; } button:nth-child(12){ font-size: 30px; background-color: #4B0082; } button:nth-child(16){ font-size: 20px; background-color: #228B22; } button:nth-child(20){ font-size: 20px; backgroun