这是之前敌人问我的一个性能：他感觉看网页有时候注意力会被转移，心愿能够有个蒙层帮忙他集中注意力
反手我就用 box-shadow 把性能写了进去。
(function(){ let lastEl = null; let styleEl = null; document.body.addEventListener('mouseover', (e)=>{ e.stopPropagation(); if(!styleEl){ styleEl = document.createElement('style'); document.body.appendChild(styleEl); styleEl.innerHTML = ` .lilnong-focus{ box-shadow: 0 0 0px 9999px rgba(0,0,0,.8); z-index: 99999; position: relative; } ` } const el = e.target; lastEl?.classList?.remove('lilnong-focus'); lastEl = el; el.classList.add('lilnong-focus'); })})()因为 z-index 无奈超过非 static 层级导致的 bug
在我测试中发现了一些比拟阳间的成果
所以咱们要小改变一下。间接给父级 ZIndex 全副晋升。
(function(){ let lastEl = null; let styleEl = null; let ZIndex = 1; document.body.addEventListener('mouseover', (e)=>{ e.stopPropagation(); if(!styleEl){ styleEl = document.createElement('style'); document.body.appendChild(styleEl); styleEl.innerHTML = ` .lilnong-focus{ box-shadow: 0 0 0px 9999px rgba(0,0,0,.8); z-index: 99999; position: relative; } ` } const el = e.target; lastEl?.classList?.remove('lilnong-focus'); lastEl = el; el.classList.add('lilnong-focus'); let parent = el; ZIndex++; while(parent){ console.log(parent?.style) if(parent.style) parent.style.zIndex = 10000 + ZIndex; parent = parent.parentNode; } }) })()因为 overflow 导致款式无奈超出盒子
那好了，咱们再把 overflow 还原一下。
(function(){ let lastEl = null; let styleEl = null; let ZIndex = 1; document.body.addEventListener('mouseover', (e)=>{ e.stopPropagation(); if(!styleEl){ styleEl = document.createElement('style'); document.body.appendChild(styleEl); styleEl.innerHTML = ` .lilnong-focus{ box-shadow: 0 0 0px 9999px rgba(0,0,0,.8); z-index: 99999; position: relative; } .lilnong ` } const el = e.target; lastEl?.classList?.remove('lilnong-focus'); lastEl = el; el.classList.add('lilnong-focus'); let parent = el; ZIndex++; while(parent){ // console.log(parent?.style) if(parent.style){ // parent.style.zIndex = 10000 + ZIndex; // overflow: visible !important; // parent.style.overflow = 'visible !important' parent.setAttribute('style', `${parent.getAttribute('style')};z-index: ${10000 + ZIndex};overflow: visible !important;`) } parent = parent.parentNode; } }) })()最佳实现？
通过咱们个别操作，终于性能能实现了。
然而这种的性能真的是咱们想要的嘛？ 咱们只是想实现一下聚焦性能，并不心愿页面布局受到毁坏。
那咱们应该怎么做呢？从下面的例子能够看到，box-shadow 是最佳的实现，他能够给咱们一个视口，将视口外的内容全副盖住，那么咱们只有管制好视口的大小即可。
这样咱们还能够对视口做一些非凡的款式解决。
当然你会说如果下面盖一层货色，会导致元素无奈选中，这里咱们能够应用 pointer-events: none; 来阻止元素接管事件。（这个罕用在头像挂件显示，一般来说单击头像是弹出资料卡。挂件咱们阻止接管事件即可。）
(function(){ let maskEl = document.querySelector('.lilnong-mask') || document.createElement('div'); maskEl.className="lilnong-mask" document.body.appendChild(maskEl); let styleEl = document.createElement('style'); document.body.appendChild(styleEl); styleEl.innerHTML = ` .lilnong-mask{ box-shadow: 0 0 0px 9999px rgba(0,0,0,.8); z-index: 99999; position: fixed; top: 0; left: 0; width: 40px; height: 40px; pointer-events: none; } ` document.body.addEventListener('mousemove', (e)=>{ e.stopPropagation(); const el = e.target; const {x,y,width,height,top,left} = el.getBoundingClientRect(); maskEl.style.left = left + 'px' maskEl.style.top = top + 'px' maskEl.style.width = width + 'px' maskEl.style.height = height + 'px' }) })()甚至说咱们还能够批改一下聚焦视口的款式
(function(){ let maskEl = document.querySelector('.lilnong-mask') || document.createElement('div'); maskEl.className="lilnong-mask" document.body.appendChild(maskEl); let styleEl = document.createElement('style'); document.body.appendChild(styleEl); styleEl.innerHTML = ` .lilnong-mask{ box-shadow: 0 0 0px 9999px rgba(0,0,0,.8); z-index: 99999; position: fixed; top: 0; left: 0; width: 40px; height: 40px; pointer-events: none; padding: 10px; box-sizing: content-box; transform: translate(-10px,-10px); border-radius: 10px } .lilnong-mask:before{ content: ''; position: absolute; top: -6px;right: -6px;bottom: -6px;left: -6px; border: 1px dashed #eee; border-radius: 10px } ` document.body.addEventListener('mousemove', (e)=>{ e.stopPropagation(); const el = e.target; const {x,y,width,height,top,left} = el.getBoundingClientRect(); maskEl.style.left = left + 'px' maskEl.style.top = top + 'px' maskEl.style.width = width + 'px' maskEl.style.height = height + 'px' }) })()因为是 left、top、width、height 的变动，所以咱们还能够 transition: .2s all; 让动画会有一个过渡成果