针对移动端自适应的几种方法集合

第一种

 (function (doc, win) {
        var docEl = doc.documentElement,
            resizeEvt = 'orientationchange' in window ? 'orientationchange' : 'resize',
            recalc = function () {
                var clientWidth = docEl.clientWidth;
                if (!clientWidth) return;
                if(clientWidth>=640){
                    docEl.style.fontSize = '100px';
                }else{
                    docEl.style.fontSize = 100 * (clientWidth / 640) + 'px';
                }
            };

        if (!doc.addEventListener) return;
        win.addEventListener(resizeEvt, recalc, false);
        doc.addEventListener('DOMContentLoaded', recalc, false);
    })(document, window);

第二种

(function (doc, win) {
  var docEl = win.document.documentElement;
  var resizeEvt = 'orientationchange' in window ? 'orientationchange' : 'resize';
  
  var refreshRem = function () {
    var clientWidth = win.innerWidth
                      || doc.documentElement.clientWidth
                      || doc.body.clientWidth;

    console.log(clientWidth)
    if (!clientWidth) return;
    var fz;
    var width = clientWidth;
    fz = 16 * width / 375;
    docEl.style.fontSize = fz + 'px';//这样每一份也是16px,即1rem=16px
  };

  if (!doc.addEventListener) return;
  win.addEventListener(resizeEvt, refreshRem, false);
  doc.addEventListener('DOMContentLoaded', refreshRem, false);
  refreshRem();

})(document, window);

第三种
网易做法：
引入：页面开头处引入下面这段代码，用于动态计算font-size

(function(doc, win) {
    var docEl = doc.documentElement,
        isIOS = navigator.userAgent.match(/\(i[^;]+;( U;)? CPU.+Mac OS X/),
        dpr = isIOS ? Math.min(win.devicePixelRatio, 3) : 1,
        dpr = window.top === window.self ? dpr : 1, //被iframe引用时，禁止缩放
        dpr = 1,
        scale = 1 / dpr,
        resizeEvt = 'orientationchange' in window ? 'orientationchange' : 'resize';
    docEl.dataset.dpr = dpr;
    var metaEl = doc.createElement('meta');
    metaEl.name = 'viewport';
    metaEl.content = 'initial-scale=' + scale + ',maximum-scale=' + scale + ', minimum-scale=' + scale;
    docEl.firstElementChild.appendChild(metaEl);
    var recalc = function() {
        var width = docEl.clientWidth;
        if (width / dpr > 750) {
            width = 750 * dpr;
        }
        // 乘以100，px : rem = 100 : 1
        docEl.style.fontSize = 100 * (width / 750) + 'px';
    };
    recalc()
    if (!doc.addEventListener) return;
    win.addEventListener(resizeEvt, recalc, false);
})(document, window);

使用：
未引入前：

body {
    width: 750px;
    height: 640px;
}

引入后：除以100并将px换成rem

body {
    width: 7.5rem;
    height: 6.4rem;
}

hotcss.js下载地址
https://github.com/huanggengzhong/hotcss

参考地址
https://segmentfault.com/a/1190000012225828?utm_source=tag-newest