javascript 控制ios textarea 不失去焦点问题

//判断是否为苹果
var isIPHONE = navigator.userAgent.toUpperCase().indexOf('IPHONE')!= -1;

// 元素失去焦点隐藏iphone的软键盘
function objBlur(id,time){
    if(typeof id != 'string') throw new Error('objBlur()参数错误');
    var obj = document.getElementById(id),
        time = time || 300,
        docTouchend = function(event){
            if(event.target!= obj){
                setTimeout(function(){
                     obj.blur();
                    document.removeEventListener('touchend', docTouchend,false);
                },time);
            }
        };
    if(obj){
        obj.addEventListener('focus', function(){
            document.addEventListener('touchend', docTouchend,false);
        },false);
    }else{
        throw new Error('objBlur()没有找到元素');
    }
}

if(isIPHONE){
    var input = new objBlur('input');
    input=null;
}