动态显示可以文本框可以输入的字数

 

<input name="title" type="text" size="50" value="{$p.title}" maxlength="15" onkeyup="javascript:setShowLength(this, 15, 'cost_tpl_title_length');"><span class="red" id="cost_tpl_title_length">还可以输入15字数</span>

function setShowLength(obj, maxlength, id){
    var rem = maxlength - obj.value.length;
    var wid = id;
    if (rem < 0){
        rem = 0;
    }
    document.getElementById(wid).innerHTML = "还可以输入" + rem + "字数";
}