手机端用rem+scss做适配的详解

html{
    font-size: 10px;
}
p{
    width: 2rem; / 210 = 20px;/
    margin: 1rem;
}

<script type="text/javascript">
    var bodyElement = document.documentElement || document.body,
        RC = {
            w: 750,
            h: 1206
        }, //默认设计稿宽高
        GC = {
            w: document.documentElement.clientWidth || window.innerWidth || screen.width,
            h: document.documentElement.clientHeight || window.innerHeight || screen.height
        };
    function setFontSize(){
        var rightSize = parseFloat((RC.w / RC.h).toFixed(1)),
            currentSize = parseFloat((GC.w / GC.h).toFixed(1)),
            lastHTMLSize = 16, // 默认16是因为html默认字号是16px
            html = document.getElementsByTagName("html")[0];
       
            if(rightSize > currentSize){  // 长屏
                lastHTMLSize = 16;
            }else if(rightSize < currentSize){  //宽屏
                lastHTMLSize = (RC.h / GC.h  GC.w) / RC.w  16;
            }
            html.style.fontSize = GC.w / lastHTMLSize + 'px';
       
    }

    setFontSize();
</script>

// 默认16是html默认字号
// 默认750是设计稿默认宽度
// $n是量取设计稿的距离

@charset "UTF-8";
@function rem($n) {
    @return $n / (750 / 16)+rem;
}

@function getTop($n) {
    @return ($n - 1206 / 2) / (750 / 16)+rem;
}

@function getLeft($n) {
    @return ($n - 750 / 2) / (750 / 16)+rem;
}

@function getRight($n) {
    @return (($n - 750) / 2) / (750 / 16)+rem;
}

@mixin center($left, $) { //左右居中 上变
    position: absolute;
    left: 50%;
    : rem($);
    margin: 0 0 0 getLeft($left);
}

@mixin centerlt($left, $) { //上下，左右居中 
    position: absolute;
    left: 50%;
    : 50%;
    margin: getTop($) 0 0 getLeft($left);
}
@mixin centerrt($right, $) { //上下，左右居中 
    position: absolute;
    right: 50%;
    : 50%;
    margin: getTop($) getRight($right) 0 0;
}
@mixin middlert($right, $) { //上下居中 右变
    position: absolute;
    right: rem($right);
    : 50%;
    margin: getTop($) 0 0 0;
}

@mixin centerb($left, $bottom) { //左右居中 下变
    position: absolute;
    left: 50%;
    bottom: rem($bottom);
    margin: 0 0 0 getLeft($left);
}

@mixin leftTop($left, $) { //左变 上变
    position: absolute;
    left: rem($left);
    : rem($);
}
@mixin rightTop($right, $) { //右变 上变
    position: absolute;
    right: rem($right);
    : rem($);
}
@mixin leftBottom($left, $bottom) { //右变 上变
    position: absolute;
    left: rem($left);
    bottom: rem($bottom);
}

.page1-img1{
    width: rem(473);
    height: rem(173);
    @include centerlt(139, 767);
}