JS 操作元素样式

const getCss = function getCss(element, attr) {  // 元素，属性
        let value = window.getComputedStyle(element)[attr],
            reg = /^\d+(px|rem|em)?$/i;
        if (reg.test(value)) {
            value = parseFloat(value);
        }
        return value;
    };
    const setCss = function setCss(element, attr, value) {
        if (attr === "opacity") {  // 元素，属性 ，值
            element['style']['opacity'] = value;
            element['style']['filter'] = `alpha(opacity=${value*100})`;
            return;
        }
        let reg = /^(width|height|margin|padding)?(top|left|bottom|right)?$/i;
        if (reg.test(attr)) {
            if (!isNaN(value)) {
                value += 'px';
            }
        }
        element['style'][attr] = value;
    };
    const setGroupCss = function setGroupCss(element, options) {
        each(options, (copy, name) => {
            setCss(element, name, copy);
        });
    };
    const css = function css(element) {
        let len = arguments.length,
            attr = arguments[1],
            value = arguments[2];
        if (len >= 3) {
            setCss(element, attr, value);
            return;
        }
        if (attr !== null && typeof attr === "object") {
            setGroupCss(element, attr);
            return;
        }
        return getCss(element, attr);
    };