rem移动端自适应

给HTML设置font-size

<script>
var viewportEl = document.querySelector('meta[name="viewport"]');
var dpr = window.devicePixelRatio || 1;
var scale = 1 / dpr;
var content = 'width=device-width, initial-scale=' + scale + ', minimum-scale=' + scale + ', maximum-scale=' + scale + ', user-scalable=no';
if (viewportEl) {
    viewportEl.setAttribute('content', content);
} else {
    viewportEl = document.createElement('meta');
    viewportEl.setAttribute('name', 'viewport');
    viewportEl.setAttribute('content', content);
    document.head.appendChild(viewportEl);
}
var innerWidth = document.documentElement.getBoundingClientRect().width || window.innerWidth;
document.documentElement.style.fontSize = ( innerWidth*20/320 ) + 'px';
</script>

使用scss将px转化成rem

@function px2rem($px){
   $rem: 640;
   @return $px*320/$rem/20 + rem;
}