<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
<head>
<meta http-equiv="Expires" content="Fri, Jan 01 1900 00:00:00 GMT">
<meta http-equiv="Pragma" content="no-cache">
<meta http-equiv="Cache-Control" content="no-cache">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<meta http-equiv="Lang" content="en">
<meta name="author" content="">
<meta http-equiv="Reply-to" content="@.com">
<meta name="generator" content="PhpED 5.6">
<meta name="description" content="">
<meta name="keywords" content="">
<meta name="creation-date" content="11/11/2008">
<meta name="revisit-after" content="15 days">
<title>Untitled</title>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js"
type="text/javascript"></script>
</head>
<body>
<form id="testform">
<input class="clear" type="text" value="Always cleared" />
<input class="clear once" type="text" value="Cleared only once" />
<input type="text" value="Normal text" />
</form>
<script type="text/javascript">
jQuery.fn.log = function (msg) {
console.log("%s: %o", msg, this);
return this;
};
$(function() {
//Go through every input field with clear class using each function
//(NB! "clear once" is two classes clear and once)
$('#testform input.clear').each(function(){
//use the data function to save the data
$(this).data( "txt", $.trim($(this).val()) );
}).focus(function(){
// On focus test for default saved value and if not the same clear it
if ( $.trim($(this).val()) === $(this).data("txt") ) {
$(this).val("");
}
}).blur(function(){
// Use blur event to reset default value in field that have class clear
// but ignore if class once is present
if ( $.trim($(this).val()) === "" && !$(this).hasClass("once") ) {
//Restore saved data
$(this).val( $(this).data("txt") );
}
});
});
var input_text = $('#shopping_cart_items input.text');
input_text
.css('border', '3px dashed yellow')
.css('background-color', 'red')
.val("text updated");
</script>
</body>
</html>
demo下载地址：https://files.cnblogs.com/ishibin/js_input%E8%AE%BE%E7%BD%AE%E9%BB%98%E8%AE%A4%E5%80%BC.rar