const inBrowser =
 typeof window !== 'undefined' &&
 Object.prototype.toString.call(window) !== '[object Object]';
export const UA = inBrowser && window.navigator.userAgent.toLowerCase();
export const isIE = UA && UA.indexOf('trident') > 0;
export const isIE9 = UA && UA.indexOf('msie 9.0') > 0;

/**
 * For IE9 compat: when both class and :class are present
 * getAttribute('class') returns wrong value...
 *
 * @param {Element} el
 * @return {String}
 */
export function getClass(el) {
 let classname = el.className;
 if (typeof classname === 'object') {
 classname = classname.baseVal || '';
 }
 return classname;
}

/**
 * 判断dom节点是否有某样式
 * 
 * @param {Element} el
 * @param {String} name
 * @return {boolean} 
 */
export function hasClass(el, name) {
 if (!el) return;
 let className = getClass(el);
 let classes = className.split('');
 return classes.indexOf(name) != -1;
}

/**
 * In IE9, setAttribute('class') will result in empty class
 * if the element also has the :class attribute; However in
 * PhantomJS, setting `className` does not work on SVG elements...
 * So we have to do a conditional check here.
 *
 * @param {Element} el
 * @param {String} cls
 */
export function setClass(el, cls) {
 /* istanbul ignore if */
 if (isIE9 && !/svg$/.test(el.namespaceURI)) {
 el.className = cls;
 } else {
 el.setAttribute('class', cls);
 }
}

/**
 * Add class with compatibility for IE & SVG
 *
 * @param {Element} el
 * @param {String} cls
 */
export function addClass(el, cls) {
 if (el.classList) {
 el.classList.add(cls);
 } else {
 let cur = '' + getClass(el) + '';
 if (cur.indexOf('' + cls + '') < 0) {
 setClass(el, (cur + cls).trim());
 }
 }
}

/**
 * Remove class with compatibility for IE & SVG
 *
 * @param {Element} el
 * @param {String} cls
 */
export function removeClass(el, cls) {
 if (el.classList) {
 el.classList.remove(cls);
 } else {
 let cur = '' + getClass(el) + '';
 let tar = '' + cls + '';
 while (cur.indexOf(tar) >= 0) {
 cur = cur.replace(tar, '');
 }
 setClass(el, cur.trim());
 }
 if (!el.className) {
 el.removeAttribute('class');
 }
}

/**
 * 从jquery扣过来的,递归去算
 *
 * @param {Element} a
 * @param {Element} b
 * @return {boolean}
 */
export function contains(a, b) {
 let adown = a.nodeType === 9 ? a.documentElement : a;
 
 let bup = b && b.parentNode;
 return a === bup || !!(bup && bup.nodeType === 1 && adown.contains(bup));
}