// 获取Element let magnifier = document.querySelector('.magnifier') let main = document.querySelector('.main') let line = document.querySelector('.line') // set click magnifier.onclick = function() { // 判断是否有class let hasOpen = magnifier.classList.contains('open') console.log(hasOpen) // 设置 class if (hasOpen) { magnifier.classList.remove('open') main.classList.remove('open') line.classList.remove('open') } else { magnifier.classList.add('open') main.classList.add('open') line.classList.add('open') } }