<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="Generator" content="EditPlus">
<meta name="Author" content="">
<meta name="Keywords" content="">
<meta name="Description" content="">
<title>输入框检测</title>
</head>
<body>
<p>只允许输入数字，否则红色警示</p>
<form action="http://localhost/index.jsp">
<input type="textarea" id="textbox">
<button type="submit" id="mybtn">提交</button>
</form>
<script>
var textbox=document.forms[0].elements[0];
//获取焦点事件
textbox.onfocus=function(){
if(textbox.style.backgroundColor != "red"){
textbox.style.backgroundColor="yellow";
}
}
//失去焦点事件
textbox.onblur=function(event){
if(/[^\d]/.test(textbox.value)){
textbox.style.backgroundColor="red";
}else{
textbox.style.backgroundColor="";
}
}
//change事件
textbox.onchange=function(event){
if(/[^\d]/.test(textbox.value)){
textbox.style.backgroundColor="red";
}else{
textbox.style.backgroundColor="";
}
}
</script>
</body>
</html>本文出自 “空空如也” 博客，请务必保留此出处http://6738767.blog.51cto.com/6728767/1583073
原文：http://6738767.blog.51cto.com/6728767/1583073