rem 是 css 的长度单位,它是相对于 <html> 元素的 font-size 的相对值。假设 html { font-size: 20px; },那么 1rem 就等于 20px。
rem布局方法1:
使用JavaScript让html的font-size随着浏览器窗口大小改变而改变
(function(designWidth, maxWidth) {
var doc = document,
win = window;
var docEl = doc.documentElement;
var tid;
var rootItem, rootStyle;
function refreshRem() {
var width = docEl.getBoundingClientRect().width;
if(!maxWidth) {
maxWidth = 540;
};
if(width > maxWidth) {
width = maxWidth;
}
//与淘宝做法不同,直接采用简单的rem换算方法1rem=100px
var rem = width * 100 / designWidth;
//兼容UC开始
rootStyle = "html{font-size:" + rem + 'px !important}';
rootItem = document.getElementById('rootsize') || document.createElement("style");
if(!document.getElementById('rootsize')) {
document.getElementsByTagName("head")[0].appendChild(rootItem);
rootItem.id = 'rootsize';
}
if(rootItem.styleSheet) {
rootItem.styleSheet.disabled || (rootItem.styleSheet.cssText = rootStyle)
} else {
try {
rootItem.innerHTML = rootStyle
} catch(f) {
rootItem.innerText = rootStyle
}
}
//兼容UC结束
docEl.style.fontSize = rem + "px";
};
refreshRem();
win.addEventListener("resize", function() {
clearTimeout(tid); //防止执行两次
tid = setTimeout(refreshRem, 300);
}, false);
win.addEventListener("pageshow", function(e) {
if(e.persisted) { // 浏览器后退的时候重新计算
clearTimeout(tid);
tid = setTimeout(refreshRem, 300);
}
}, false);
if(doc.readyState === "complete") {
doc.body.style.fontSize = "16px";
} else {
doc.addEventListener("DOMContentLoaded", function(e) {
doc.body.style.fontSize = "16px";
}, false);
}
})(750, 750);
rem布局方法2:
html {
font-size: 10px
}
@media screen and (min-width:321px) and (max-width:375px) {
html {
font-size: 11px
}
}
@media screen and (min-width:376px) and (max-width:414px) {
html {
font-size: 12px
}
}
@media screen and (min-width:415px) and (max-width:639px) {
html {
font-size: 15px
}
}
@media screen and (min-width:640px) and (max-width:719px) {
html {
font-size: 20px
}
}
@media screen and (min-width:720px) and (max-width:749px) {
html {
font-size: 22.5px
}
}
@media screen and (min-width:750px) and (max-width:799px) {
html {
font-size: 23.5px
}
}
@media screen and (min-width:800px) {
html {
font-size: 25px
}
}