input输入框，你还可以输入多少字？window.var oSpan = document.var oText = d

localStorage应用

<!doctype html>
<html>
<head>
<meta charset="utf-8">
<meta name="author" content="和派孔明" />
<meta name="copyright" content="和派孔明" />
<title>你还可以输入多少字</title>
<style>
</style>
<script>
window.onload = function(){
    var oSpan = document.getElementById("s1");
    var oText = document.getElementById("txt1");    
    var total = 5;
    var msg = localStorage.msg;
    if(msg){
        oText.value = msg;  
        var len = total - oText.value.length;
        if(len >= 0){
            oSpan.innerHTML = "你还可以输入<strong>"+len+"</strong>个字！";  
        } else {//超出
            oSpan.innerHTML = "你已超出<strong style='color:red;'>"+Math.abs(len)+"</strong>个字！";   
        }
    }

    oText.oninput = function(){ 
        localStorage.msg = this.value;  
        var len = total - this.value.length;    
        if(len >= 0){
            oSpan.innerHTML = "你还可以输入<strong>"+len+"</strong>个字！";  
        } else {//超出
            oSpan.innerHTML = "你已超出<strong style='color:red;'>"+Math.abs(len)+"</strong>个字！";   
        }
    };
};
</script>
</head>

<body>
<span id="s1">你还可以输入<strong>5</strong>个字！</span><br /><br />
<textarea id="txt1" style="width:500px; height:300px;"></textarea>

</body>
</html>