彈出框 背景固定 滑動

// 彈出框 背景滑動問題 style.cssText 彈出框父級absolute body fixed  彈出框absolute 也是一種解決方案
val 變量，當前彈出框狀態
      huaDong (val) {
        let scrollTop = 0
        if (document.scrollingElement) {
          scrollTop = document.scrollingElement.scrollTop
        } else {
          scrollTop = document.documentElement.scrollTop || document.body.scrollTop || window.pageYOffset || 0
        }
        const bodyTag = window.document.getElementsByTagName('body')[0]
        val ? bodyTag.classList.add('com-mask-background') : bodyTag.classList.remove('com-mask-background')
        val ? bodyTag.style.top = -scrollTop + 'px' : window.scrollTo(0, -parseInt(bodyTag.style.top, 10))
      },

css

.com-mask-background {
        position: fixed;
        height: 100%;
        width: 100%;
        overflow: hidden;
    }