<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
</head>
<body>
<h1>JavaScript 数字验证</h1>
<p>只能输入数字：</p>
<input id="numb" >
<button type="button" onclick="myFunction()">提交</button>
<p id="demo"></p>
<script>
function myFunction() {
var x, text;
// 获取 id="numb" 的值
x = document.getElementById("numb").value;
console.log(x);
// 如果输入的值 x 不是数字或者为空 则提示
if (isNaN(x) ) {
text = "请不要乱输,输入数字";
} else if ( x.length ===0){//判断是否有输入内容
text = "请输入内容";
}
else {
text = "正确";
}
document.getElementById("demo").innerHTML = text;//八提示文本内容显示出来
}
</script>
</body>
</html><!DOCTYPE html>
