如何获取隐藏元素的宽高

//获取元素的物理尺寸，参数：element隐藏的元素节点;targetEl需要获取尺寸的目标元素
this.getSize = function(element,targetEl) {
    //增加隐藏，防止element在取消隐藏时闪烁; position: absolute;和display:none看需要是否加上
    var _addCss = { visibility: ‘hidden‘ };
    var _oldCss = {};
    var _width;
    var _height;
    if (this.getStyle(element, "display") != "none") {
        return { width: !!targetEl ? targetEl.offsetWidth  : element.offsetWidth , height: !!targetEl ? targetEl.offsetHeight : element.offsetHeight };
    }
    for (var i in _addCss) {
        _oldCss[i] = this.getStyle(element, i);
    }
    this.setStyle(element, _addCss);
    //这里是通过angularjs的ng-show指令隐藏元素的，去掉ng-hide样式类就可以取消隐藏
    var _isNgHide = element.classList.contains("ng-hide");
    _isNgHide && element.classList.remove("ng-hide");
    _width = !!targetEl ? targetEl.offsetWidth  : element.offsetWidth;
    _height =!!targetEl ? targetEl.offsetHeight : element.offsetHeight;
    //还原之前的样式，class
    this.setStyle(element, _oldCss);
    _isNgHide && element.classList.add("ng-hide");
    return { width: _width, height: _height };
};

this.getStyle = function(element, styleName) {
    return element.style[styleName] ? element.style[styleName] : element.currentStyle ? element.currentStyle[styleName] : window.getComputedStyle(element, null)[styleName];
};

this.setStyle = function(element, obj){
    if (angular.isObject(obj)) {
        for (var property in obj) {
            var cssNameArr = property.split("-");
            for (var i = 1,len=cssNameArr.length; i < len; i++) {
                cssNameArr[i] = cssNameArr[i].replace(cssNameArr[i].charAt(0), cssNameArr[i].charAt(0).toUpperCase());
            }
            var cssName = cssNameArr.join("");
            element.style[cssName] = obj[property];
        }
    }
    else if (angular.isString(obj)) {
        element.style.cssText = obj;
    }
};