<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<style>
.gg{
color:#dddddd; (浅灰色)
}
.bb{
color:black; (黑色的字体)
}
</style>
</head>
<body>
<input type="text" class="gg" value="请输入内容" onfocus="Focus(this);" onblur="Blur(this);"/>
<script>
function Focus(ths){
//查找第一种方式
//document
//第二种方式 (this)
//ths
ths.className = "bb";
var current_val = ths.value;
if(current_val == "请输入内容"){
ths.value = ""
}
}
function Blur(ths){
var current_val = ths.value;
if(current_val == "请输入内容" || current_val.trim().length == 0){
ths.value = "请输入内容";
ths.className == "gg";
}
}
</script>
</body>
