function checkLen(obj) {
var maxChars = 50;//最多字符数
//判断超过50直接清除多的并弹框
if (obj.value.length > maxChars) alert('不能超过50个字'); obj.value = obj.value.substring(0,maxChars);
var curr = maxChars - obj.value.length;
document.getElementByIdx_x("count").innerHTML = curr.toString();
}