javascript - 检查输入的是数字还是字母javascript(Check if input is number or letter javascript)

Question

I'm using forms in HTML and javascript.(我正在使用HTML和javascript中的表单。)

I would like an alert to pop up only if the user inputs a LETTER and clicks submit .(我想一个警告弹出只有当用户输入一个字母 ，点击submit 。) So I have the HTML code:(所以我有HTML代码：) <form name="myForm" action="" onsubmit="return checkInp()" method="post"> First name: <input type="text" name="age"> <input type="submit" value="Submit"> And the javascript code:(和javascript代码：) function checkInp() { var x=document.forms["myForm"]["age"].value; if (x consists of any letters) // this is the code I need to change { alert("Must input numbers"); return false; } }   ask by Greg Peckory translate from so

Answer 1

You can use the isNaN function to determine if a value does not convert to a number.(您可以使用isNaN函数确定值是否不转换为数字。)

Example as below:(示例如下：) function checkInp() { var x=document.forms["myForm"]["age"].value; if (isNaN(x)) { alert("Must input numbers"); return false; } }