js获取网页字体大小

let rootFontSize = window.getComputedStyle(document.documentElement).fontSize;
console.log(rootFontSize); // 输出全局字体大小，例如："16px"

let element = document.getElementById('myElement');
let elementFontSize = window.getComputedStyle(element).fontSize;
console.log(elementFontSize); // 输出特定元素的字体大小，例如："14px"

#myElement {
  font-size: 16px; /* 设置一个明确的字体大小 */
}

/* 简单的CSS重置 */
html, body, div, span, applet, object, iframe,
h1, h2, h3, h4, h5, h6, p, blockquote, pre,
a, abbr, acronym, address, big, cite, code,
del, dfn, em, img, ins, kbd, q, s, samp,
small, strike, strong, sub, sup, tt, var,
b, u, i, center,
dl, dt, dd, ol, ul, li,
fieldset, form, label, legend,
table, caption, tbody, tfoot, thead, tr, th, td,
article, aside, canvas, details, embed, 
figure, figcaption, footer, header, hgroup, 
menu, nav, output, ruby, section, summary,
time, mark, audio, video {
  margin: 0;
  padding: 0;
  border: 0;
  font-size: 100%;
  font: inherit;
  vertical-align: baseline;
}