Vant+postcss-pxtorem implements browser adaptation function

npm install postcss-pxtorem --save

module.exports = {
 "plugins": {
 	//"postcss-import": {},
  //"postcss-url": {},
  "autoprefixer": {
   browsers: ['Android >= 4.0', 'iOS >= 7']
  },
  "postcss-pxtorem": {
   "rootValue": 32,
   "propList": ["*"]
  }
 }
}

const baseSize = 32
// Set rem function function setRem () {
 // The scaling ratio of the current page width relative to 750 width, which can be modified according to your needs.
 const scale = document.documentElement.clientWidth / 750
 // Set the font size of the root node of the page document.documentElement.style.fontSize = (baseSize * Math.min(scale, 2)) + 'px'
}
// Initialize setRem()
// Reset rem when changing window size
window.onresize = function () {
 setRem()
}

import "./rem.js"

(function (doc, win) {
 var docEl = doc.documentElement
 var resizeEvt = 'orientationchange' in window ? 'orientationchange' : 'resize'
 var recalc = function () {
  var clientWidth = docEl.clientWidth
  if (!clientWidth) return
  if (parseInt(20 * (clientWidth / 320)) > 35) {
   docEl.style.fontSize = 35 + 'px'
  } else {
   docEl.style.fontSize = 20 * (clientWidth / 320) + 'px'
  }
 }
 if (!doc.addEventListener) return
 win.addEventListener(resizeEvt, recalc, false)
 doc.addEventListener('DOMContentLoaded', recalc, false)
})(document, window)

import "./rem.js"

// The scaling ratio of the current page width relative to 750 width, which can be modified according to your needs.
$rem: (640/750)/40;
body{
	width: $rem * 24rem;
}