為了方便以後讓任何網站都能快速擁有回頂部按鈕，特別寫了一個結合 HTML、CSS、JavaScript 和 jQuery 的回頂部按鈕，輕鬆就能使用！基本上只要在網頁 <head> 到 </head> 中先引入 jQuery 後即可直接使用。通常這種設計是為了方便讓使用者在看完網頁主要內容後，能快速回到最上面查看導覽列，若您的網站本身就設有固定於頂部的導覽列，可能就比較不需要這種設計。
接著就讓我們直接來看看原始碼吧！首先是 HTML：
<div class="back-top hide" title="回頂部"></div>這段只要放在 <body> 到 </body> 中的任何地方即可！再來是 CSS：
.back-top {
z-index: 99999;
position: fixed;
bottom: 5px;
right: 5px;
cursor: pointer;
opacity: 0.5;
filter: Alpha(opacity=50);
width: 35px;
height: 35px;
background: #000 center no-repeat
url(data:image/svg+xml;base64,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);
background-size: 24px 24px;
border-radius: 12px;
border: 1px rgba(255, 255, 255, 0.6) solid;
box-shadow: 0px 0px 3px #ffffff;
transform: translateY(0%);
transition: all 0.2s linear;
}
.back-top:hover {
opacity: 0.8;
filter: Alpha(opacity=80);
box-shadow: 0px 0px 6px #ffffff;
}
.back-top.hide {
opacity: 0;
filter: Alpha(opacity=0);
transform: translateY(150%);
}我已經將按鈕中的 SVG 向量圖示用 base64 編碼寫入在 CSS 中，另外也設計了動畫效果，讓按鈕更美觀且精緻！最後來看 JavaScript 和 jQuery 的部分：
$(document).ready(function () {
// 捲軸偵測距離頂部超過 50 才顯示按鈕
$(window).scroll(function () {
if ($(window).scrollTop() > 50) {
if ($(".back-top").hasClass("hide")) {
$(".back-top").toggleClass("hide");
}
} else {
$(".back-top").addClass("hide");
}
});
// 點擊按鈕回頂部
$(".back-top").on("click", function (event) {
$("html, body").animate(
{
scrollTop: 0
},
500 // 回頂部時間為 500 毫秒
);
});
});透過註解，我已經將兩段程式碼主要做的事情告知給您啦！前面基本上是要讓網頁已經是在最上面時不要顯示出按鈕，後面基本上就是點了按鈕後會花指定的時間滾動到頂部，很容易理解吧！下面有預覽可以直接看～
CodePen
See the Pen
Untitled by Feng, Cheng-Chi (@qwe987299)
on CodePen.
▲ 精選圖片。
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