```js const trim = function (string) { return (string || '').replace(/^[\s\uFEFF]+|[\s\uFEFF]+$/g, '') } // 查找某個class類 export function hasClass (el, cls) { if (!el || !cls) return false if (cls.indexOf(' ') !== -1) throw new Error('className should not contain space.') if (el.classList) { return el.classList.contains(cls) } return (` ${el.className} `).indexOf(` ${cls} `) > -1 } // 添加某個class類 export function addClass (el, cls) { if (!el) return const classes = (cls || '').split(' ') let curClass = el.className for (let i = 0, j = classes.length; i < j; i++) { const clsName = classes[i] if (!clsName) continue if (el.classList) { el.classList.add(clsName) } else if (!hasClass(el, clsName)) { curClass += ` ${clsName}` } } if (!el.classList) { el.className = curClass } } // 移出某個class類 export function removeClass (el, cls) { if (!el || !cls) return const classes = cls.split(' ') let curClass = ` ${el.className} ` for (let i = 0, j = classes.length; i < j; i++) { const clsName = classes[i] if (!clsName) continue if (el.classList) { el.classList.remove(clsName) } else if (hasClass(el, clsName)) { curClass = curClass.replace(` ${clsName} `, ' ') } } if (!el.classList) { el.className = trim(curClass) } } ```