Native js settings rem

The use of rem is for the interface to respond to mobile phones of different sizes. The following method can be used to use rem.

 setFontSize: function (doc, win) {
    var docEl = doc.documentElement
    var resizeEvt = 'orientationchange' in window ? 'orientationchange' : 'resize'
    var reCaculate = function () {
    var clientWidth = docEl.clientWidth
    if (!clientWidth) return
      docEl.style.fontSize = 100 * (clientWidth / 750) + 'px'
    }
    if (!doc.addEventListener) return
    win.addEventListener(resizeEvt, reCaculate, false)
    doc.addEventListener('DOMContentLoaded', reCaculate, false)
  },

Code using this method:

this.setFontSize(document, window)