// ==UserScript==
// @name         scrollfix
// @version      0.0.1
// @namespace    tsharp.js
// @description  JQuery辅助文本框在浏览器中固定位置，不随浏览器滚动条滚动
// @author       jimbo
// @license      GPLv3
// @match        *
// @icon         none
// @require      http://code.jquery.com/jquery-3.4.1.min.js
// ==/UserScript==
; (function ($) {
jQuery.fn.scrollFix = function (height, dir) {
height = height || 0;
height = height == "top" ? 0 : height;
return this.each(function () {
if (height == "bottom") {
height = document.documentElement.clientHeight - this.scrollHeight;
} else if (height < 0) {
height = document.documentElement.clientHeight - this.scrollHeight + height;
}
var that = $(this),
oldHeight = false,
p, r, l = that.offset().left;
dir = dir == "bottom" ? dir : "top"; //默认滚动方向向下
if (window.XMLHttpRequest) { //非ie6用fixed
function getHeight() { //>=0表示上面的滚动高度大于等于目标高度
return (document.documentElement.scrollTop || document.body.scrollTop) + height - that.offset().top;
}
$(window).scroll(function () {
if (oldHeight === false) {
if ((getHeight() >= 0 && dir == "top") || (getHeight() <= 0 && dir == "bottom")) {
oldHeight = that.offset().top - height;
that.css({
position: "fixed",
top: height,
left: l
});
}
} else {
if (dir == "top" && (document.documentElement.scrollTop || document.body.scrollTop) < oldHeight) {
that.css({
position: "fixed"
});
oldHeight = false;
} else if (dir == "bottom" && (document.documentElement.scrollTop || document.body.scrollTop) > oldHeight) {
that.css({
position: "fixed"
});
oldHeight = false;
}
}
});
} else { //for ie6
$(window).scroll(function () {
if (oldHeight === false) { //恢复前只执行一次，减少reflow
if ((getHeight() >= 0 && dir == "top") || (getHeight() <= 0 && dir == "bottom")) {
oldHeight = that.offset().top - height;
r = document.createElement("span");
p = that[0].parentNode;
p.replaceChild(r, that[0]);
document.body.appendChild(that[0]);
that[0].style.position = "absolute";
}
} else if ((dir == "top" && (document.documentElement.scrollTop || document.body.scrollTop) < oldHeight) || (dir == "bottom" && (document.documentElement.scrollTop || document.body.scrollTop) > oldHeight)) { //结束
that[0].style.position = "absolute";
p.replaceChild(that[0], r);
r = null;
oldHeight = false;
} else { //滚动
that.css({
left: l,
top: height + document.documentElement.scrollTop
})
}
});
}
});
};
})(jQuery);