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rem & 16px & 62.5%

1. 浏览器的默认字体大小都是16px

2. 兼容性：IE9+，Firefox、Chrome、Safari、Opera 的主流版本都支持了rem

3. 对不支持的浏览器，应对方法也很简单，就是多写一个绝对单位的声明，这些浏览器会忽略用rem设定的字体大小;

4. rem 是只相对于根元素htm的 font-size，即只需要设置根元素的font-size，其它元素使用rem单位设置成相应的百分比即可;

css solution

@charset "UTF-8";

/* rem & 16px */
/* 100% === 16px => 1px === 6.25% => 10px === 62.5% */
/* 1rem === 10px */
html {
  font-size: 62.5%;
}

body {
  /* rem fallback */
  font-size: 12px;
  font-size: 1.2rem;
}

p {
  /* rem fallback */
  font-size: 14px;
  font-size: 1.4rem;
}

H5 移动端适配

响应式

/* media query */

@media only screen and (min- 320px){
  html {
    font-size: 62.5% !important;
  }
}
@media only screen and (min- 640px){
  html {
    font-size: 125% !important;
  }
}
@media only screen and (min- 750px){
  html {
    font-size: 150% !important;
  }
}
@media only screen and (min- 1242px){
  html {
    font-size: 187.5% !important;
  }
}

js solution

js 动态设置根字体

px-to-rem.js

//适配不同尺寸
(function(doc, win) {
    var docEl = doc.documentElement,
        resizeEvt = 'orientationchange' in window ? 'orientationchange' : 'resize',
        recalc = function() {
            var clientWidth = docEl.clientWidth;
            if (!clientWidth) return;
            // default 16px = 1rem; => 1px = 1/16rem (0.0625rem);
            docEl.style.fontSize = 100 * (clientWidth / 750) + 'px';
            // 750px PS & customized 100px = 1rem; => 1px = 1/100rem(0.01rem);
        };
    if (!doc.addEventListener) return;
    win.addEventListener(resizeEvt, recalc, false);
    doc.addEventListener('DOMContentLoaded', recalc, false);
})(document, window);

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