我将脚本smoothscroll.js加载到tampermonkey。 tampermonkey IDE显示该脚本有很多错误，但脚本工作得很好。但是，我决定修复这些错误，这很容易（缺少分号，缺少()和其他一些问题）。
但是，我很难解决以下错误。有一个do-while循环，其赋值为条件表达式。
function overflowingAncestor(el) {
var elems = [];
var rootScrollHeight = root.scrollHeight;
do {
var cached = cache[uniqueID(el)];
if (cached) {
return setCache(elems, cached);
}
elems.push(el);
if (rootScrollHeight === el.scrollHeight) {
if (!isFrame || root.clientHeight + 10 < rootScrollHeight) {
return setCache(elems, document.body);
}
} else if (el.clientHeight + 10 < el.scrollHeight) {
overflow = getComputedStyle(el, "").getPropertyValue("overflow-y");
if (overflow === "scroll" || overflow === "auto") {
return setCache(elems, el);
}
}
} while (el = el.parentNode); //<--- Error
}
我认为修复只是将while (el = el.parentNode);替换为while (el == el.parentNode);，但应用此功能后，smoothscroll将不再有效。
我知道我可以让它像它一样，但我试着理解为什么错误被抛出，即使它正在工作？
如果您想现场试用，请转到this page并将以下脚本加载到您的篡改引擎。
// ==UserScript==
// @name Test
// @namespace http://bs.to/
// @version 2.2
// @description Test
// @author Me
// @match https://bs.to/andere-serien
// @require https://code.jquery.com/jquery-3.3.1.min.js
// ==/UserScript==
//Smoothscroll.js
(function() {
var defaultOptions = {
frameRate: 300,
animationTime: 1500,
stepSize: 120,
pulseAlgorithm: true,
pulseScale: 8,
pulseNormalize: 1,
accelerationDelta: 20,
accelerationMax: 1,
keyboardSupport: true,
arrowScroll: 50,
touchpadSupport: true,
fixedBackground: true,
excluded: ""
};
var options = defaultOptions;
var isExcluded = false;
var isFrame = false;
var direction = {
x: 0,
y: 0
};
var initDone = false;
var root = document.documentElement;
var activeElement;
var observer;
var deltaBuffer = [120, 120, 120];
var key = {
left: 37,
up: 38,
right: 39,
down: 40,
spacebar: 32,
pageup: 33,
pagedown: 34,
end: 35,
home: 36
};
options = defaultOptions;
function initTest() {
var disableKeyboard = false;
if (disableKeyboard) {
removeEvent("keydown", keydown);
}
if (options.keyboardSupport && !disableKeyboard) {
addEvent("keydown", keydown);
}
}
function init() {
if (!document.body)
return;
var body = document.body;
var html = document.documentElement;
var windowHeight = window.innerHeight;
var scrollHeight = body.scrollHeight;
root = (document.compatMode.indexOf('CSS') >= 0) ? html : body;
activeElement = body;
initTest();
initDone = true;
if (top != self) {
isFrame = true;
} else if (scrollHeight > windowHeight && (body.offsetHeight <= windowHeight || html.offsetHeight <= windowHeight)) {
var pending = false;
var refresh = function() {
if (!pending && html.scrollHeight != document.height) {
pending = true;
setTimeout(function() {
html.style.height = document.height + 'px';
pending = false;
}, 500);
}
};
html.style.height = 'auto';
setTimeout(refresh, 10);
if (root.offsetHeight <= windowHeight) {
var underlay = document.createElement("div");
underlay.style.clear = "both";
body.appendChild(underlay);
}
}
if (!options.fixedBackground && !isExcluded) {
body.style.backgroundAttachment = "scroll";
html.style.backgroundAttachment = "scroll";
}
}
var que = [];
var pending = false;
var lastScroll = +new Date();
function scrollArray(elem, left, top, delay) {
if (delay === undefined) {
delay = 1000;
}
directionCheck(left, top);
if (options.accelerationMax != 1) {
var now = +new Date();
var elapsed = now - lastScroll;
if (elapsed < options.accelerationDelta) {
var factor = (1 + (30 / elapsed)) / 2;
if (factor > 1) {
factor = Math.min(factor, options.accelerationMax);
left *= factor;
top *= factor;
}
}
lastScroll = +new Date();
}
que.push({
x: left,
y: top,
lastX: (left < 0) ? 0.99 : -0.99,
lastY: (top < 0) ? 0.99 : -0.99,
start: +new Date()
});
if (pending) {
return;
}
var scrollWindow = (elem === document.body);
var step = function(time) {
var now = +new Date();
var scrollX = 0;
var scrollY = 0;
for (var i = 0; i < que.length; i++) {
var item = que[i];
var elapsed = now - item.start;
var finished = (elapsed >= options.animationTime);
var position = (finished) ? 1 : elapsed / options.animationTime;
if (options.pulseAlgorithm) {
position = pulse(position);
}
var x = (item.x * position - item.lastX) >> 0;
var y = (item.y * position - item.lastY) >> 0;
scrollX += x;
scrollY += y;
item.lastX += x;
item.lastY += y;
if (finished) {
que.splice(i, 1);
i--;
}
}
if (scrollWindow) {
window.scrollBy(scrollX, scrollY);
} else {
if (scrollX)
elem.scrollLeft += scrollX;
if (scrollY)
elem.scrollTop += scrollY;
}
if (!left && !top) {
que = [];
}
if (que.length) {
requestFrame(step, elem, (delay / options.frameRate + 1));
} else {
pending = false;
}
};
requestFrame(step, elem, 0);
pending = true;
}
function wheel(event) {
if (!initDone) {
init();
}
var target = event.target;
var overflowing = overflowingAncestor(target);
if (!overflowing || event.defaultPrevented || isNodeName(activeElement, "embed") || (isNodeName(target, "embed") && /\.pdf/i.test(target.src))) {
return true;
}
var deltaX = event.wheelDeltaX || 0;
var deltaY = event.wheelDeltaY || 0;
if (!deltaX && !deltaY) {
deltaY = event.wheelDelta || 0;
}
if (!options.touchpadSupport && isTouchpad(deltaY)) {
return true;
}
if (Math.abs(deltaX) > 1.2) {
deltaX *= options.stepSize / 120;
}
if (Math.abs(deltaY) > 1.2) {
deltaY *= options.stepSize / 120;
}
scrollArray(overflowing, -deltaX, -deltaY);
event.preventDefault();
}
function keydown(event) {
var target = event.target;
var modifier = event.ctrlKey || event.altKey || event.metaKey || (event.shiftKey && event.keyCode !== key.spacebar);
if (/input|textarea|select|embed/i.test(target.nodeName) || target.isContentEditable || event.defaultPrevented || modifier) {
return true;
}
if (isNodeName(target, "button") && event.keyCode === key.spacebar) {
return true;
}
var shift, x = 0,
y = 0;
var elem = overflowingAncestor(activeElement);
var clientHeight = elem.clientHeight;
if (elem == document.body) {
clientHeight = window.innerHeight;
}
switch (event.keyCode) {
case key.up:
y = -options.arrowScroll;
break;
case key.down:
y = options.arrowScroll;
break;
case key.spacebar:
shift = event.shiftKey ? 1 : -1;
y = -shift * clientHeight * 0.9;
break;
case key.pageup:
y = -clientHeight * 0.9;
break;
case key.pagedown:
y = clientHeight * 0.9;
break;
case key.home:
y = -elem.scrollTop;
break;
case key.end:
var damt = elem.scrollHeight - elem.scrollTop - clientHeight;
y = (damt > 0) ? damt + 10 : 0;
break;
case key.left:
x = -options.arrowScroll;
break;
case key.right:
x = options.arrowScroll;
break;
default:
return true;
}
scrollArray(elem, x, y);
event.preventDefault();
}
function mousedown(event) {
activeElement = event.target;
}
var cache = {};
setInterval(function() {
cache = {};
}, 10 * 1000);
var uniqueID = (function() {
var i = 0;
return function(el) {
return el.uniqueID || (el.uniqueID = i++);
};
})();
function setCache(elems, overflowing) {
for (var i = elems.length; i--;)
cache[uniqueID(elems[i])] = overflowing;
return overflowing;
}
function overflowingAncestor(el) {
var elems = [];
var rootScrollHeight = root.scrollHeight;
do {
var cached = cache[uniqueID(el)];
if (cached) {
return setCache(elems, cached);
}
elems.push(el);
if (rootScrollHeight === el.scrollHeight) {
if (!isFrame || root.clientHeight + 10 < rootScrollHeight) {
return setCache(elems, document.body);
}
} else if (el.clientHeight + 10 < el.scrollHeight) {
overflow = getComputedStyle(el, "").getPropertyValue("overflow-y");
if (overflow === "scroll" || overflow === "auto") {
return setCache(elems, el);
}
}
} while (el = el.parentNode);
}
function addEvent(type, fn, bubble) {
window.addEventListener(type, fn, (bubble || false));
}
function removeEvent(type, fn, bubble) {
window.removeEventListener(type, fn, (bubble || false));
}
function isNodeName(el, tag) {
return (el.nodeName || "").toLowerCase() === tag.toLowerCase();
}
function directionCheck(x, y) {
x = (x > 0) ? 1 : -1;
y = (y > 0) ? 1 : -1;
if (direction.x !== x || direction.y !== y) {
direction.x = x;
direction.y = y;
que = [];
lastScroll = 0;
}
}
var deltaBufferTimer;
function isTouchpad(deltaY) {
if (!deltaY)
return;
deltaY = Math.abs(deltaY);
deltaBuffer.push(deltaY);
deltaBuffer.shift();
clearTimeout(deltaBufferTimer);
var allDivisable = (isDivisible(deltaBuffer[0], 120) && isDivisible(deltaBuffer[1], 120) && isDivisible(deltaBuffer[2], 120));
return !allDivisable;
}
function isDivisible(n, divisor) {
return (Math.floor(n / divisor) == n / divisor);
}
var requestFrame = (function() {
return window.requestAnimationFrame || window.webkitRequestAnimationFrame || function(callback, element, delay) {
window.setTimeout(callback, delay || (1000 / 60));
};
})();
function pulse_(x) {
var val, start, expx;
x = x * options.pulseScale;
if (x < 1) {
val = x - (1 - Math.exp(-x));
} else {
start = Math.exp(-1);
x -= 1;
expx = 1 - Math.exp(-x);
val = start + (expx * (1 - start));
}
return val * options.pulseNormalize;
}
function pulse(x) {
if (x >= 1)
return 1;
if (x <= 0)
return 0;
if (options.pulseNormalize == 1) {
options.pulseNormalize /= pulse_(1);
}
return pulse_(x);
}
var isChrome = /chrome/i.test(window.navigator.userAgent);
var wheelEvent = null;
if ("onwheel" in document.createElement("div"))
wheelEvent = "wheel";
else if ("onmousewheel" in document.createElement("div"))
wheelEvent = "mousewheel";
if (wheelEvent && isChrome) {
addEvent(wheelEvent, wheel);
addEvent("mousedown", mousedown);
addEvent("load", init);
}
})();
答案 0 :(得分：2)
要使linter满意，请将作业移至while之前的行，然后while(el)
do {
// snip
el = el.parentNode;
} while (el);
替代地
do {
// snip
} while ((el = el.parentNode));
不确定所有“linters”是否会很好用，但jshint通常会
答案 1 :(得分：1)
我不熟悉tampermonkey，但是根据你的描述，它似乎比JavaScript解析器更严格。无论如何，要理解为什么while (el = el.parentNode)有效，你需要知道两件事。
（1）JavaScript中的条件（if，while中使用的条件以及传统for循环的第二个表达式）不必是严格的布尔表达式，例如x == 1。它们可以是你喜欢的任何表达方式。 JavaScript将评估该表达式，然后确定结果是否为＆＃34; truthy＆＃34;或＆＃34; falsy＆＃34; （那些是实际的话）。 A＆＃34; falsy＆＃34;值为false，null，undefined，0或空字符串。任何其他价值都是＆＃34; truthy＆＃34; （包括空数组或空对象）。 Truthy值意味着将执行if分支，或者在您的情况下，循环将继续。
（2）JavaScript中的值赋值是一个类似于任何其他表达式的表达式，并且表达式总是有结果。在值赋值的情况下，它是指定的值。严格来说，左侧变量最终包含指定值的事实是＆＃34;副作用＆＃34;。
考虑到这两个事实，这里发生了while (el = el.parentNode)：
el.parentNode。这可能是一个节点，如果null没有父级，则为el。（如果它是文档本身）。el.parentNode的值已分配给el。分配的值的此操作的结果。el没有父级，则el.parentNode为null，这是一个假值，因此循环停止。如果不是，则循环继续。因此，JavaScript允许条件中的变量赋值，但似乎tampermonkey没有。这可能是因为99％的时间您确实希望在条件中使用==，并且很容易意外地输入=而不是==。这可能导致很多挫折和难以发现的错误，因为如上所述，JavaScript会愉快地处理它而不会出错，因此很多短语都会将其标记为错误。
此外，el == el.parentNode没有意义，因为节点永远不能与其父节点相等。