Use a regular expression match is a number, directly on the demo
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <meta http-equiv="X-UA-Compatible" content="ie=edge"> <title>checkNumber</title> </head> <body style="background-color: aliceblue;"> <div id="main" style="margin: 0 auto; text-align: center; "> <form method="POST" action="" style="width: 50% ; height: 50%; text-align: center;margin: 0 auto; padding-top: 20%;"> <label>請輸入判斷的數字：</label><input type="text" id="amount" name="amount" onblur="checkAmount('amount','hint')" /><br /> <p><span name="hint" id="hint" style="color: red"></span></p> </form> </div> </body> <script src="https://code.jquery.com/jquery-3.1.1.min.js"></script> <script type="text/javascript"> $(function () { //設置div高度 $("#main").css("height", $(document).height); $("#main " ) .css ( " width " , $ (Document) .width); }); function notIntOrDecimal (text) { // check (decimal / numeric) regex the let pattern = / ^ [0-9] + (. 1} {[0-9] + [.]) $ {0,1} / ; IF (pattern.test (text)) { return to false ; } the else { return to true ; } } function checkAmount (the objName, hintName ) { the let judgeVal = $ ( " # " + The objName) .val (); IF (judgeVal ! == '' && notIntOrDecimal (judgeVal)) { $ ( " # " + hintName) .html ( " Please enter an integer or decimal! " ); $ ( " # " + the objName) .focus (); } the else { $ ( " # " + hintName) .html ( " the verification is successful! " ); } } </ Script > </ HTML >