权限没有,则隐藏 function forum_list_access_filter($forumlist, $gid, $allow = 'allowread') { global $grouplist; if (empty($forumlist)) return array(); if (1 == $gid) return $forumlist; $forumlist_filter = $forumlist; $group = $grouplist[$gid]; foreach ($forumlist_filter as $fid => $forum) { if (empty($forum['accesson']) && empty($group[$allow]) || !empty($forum['accesson']) && empty($forum['accesslist'][$gid][$allow])) { unset($forumlist_filter[$fid]); } unset($forumlist_filter[$fid]['accesslist']); } return $forumlist_filter; } function forum_filter_moduid($moduids) { $moduids = trim($moduids); if (empty($moduids)) return ''; $arr = explode(',', $moduids); $r = array(); foreach ($arr as $_uid) { $_uid = intval($_uid); $_user = user_read($_uid); if (empty($_user)) continue; if ($_user['gid'] > 4) continue; $r[] = $_uid; } return implode(',', $r); } function forum_safe_info($forum) { //unset($forum['moduids']); return $forum; } function forum_filter($forumlist) { foreach ($forumlist as &$val) { unset($val['brief'], $val['announcement'], $val['seo_title'], $val['seo_keywords'], $val['create_date_fmt'], $val['icon_url'], $val['modlist']); } return $forumlist; } function forum_format_url($forum) { global $conf; if (0 == $forum['category']) { // 列表URL $url = url('list-' . $forum['fid'], '', FALSE); } elseif (1 == $forum['category']) { // 频道 $url = url('category-' . $forum['fid'], '', FALSE); } elseif (2 == $forum['category']) { // 单页 $url = url('read-' . trim($forum['brief']), '', FALSE); } if ($conf['url_rewrite_on'] > 1 && $forum['well_alias']) { if (0 == $forum['category'] || 1 == $forum['category']) { $url = url($forum['well_alias'], '', FALSE); } elseif (2 == $forum['category']) { // 单页 $url = ($forum['threads'] && $forum['brief']) ? url($forum['well_alias'] . '-' . trim($forum['brief']), '', FALSE) : url($forum['well_alias'], '', FALSE); } } return $url; } function well_forum_alias() { $forumlist = forum_list_cache(); if (empty($forumlist)) return ''; $key = 'forum-alias'; static $cache = array(); if (isset($cache[$key])) return $cache[$key]; $cache[$key] = array(); foreach ($forumlist as $val) { if ($val['well_alias']) $cache[$key][$val['fid']] = $val['well_alias']; } return array_flip($cache[$key]); } function well_forum_alias_cache() { global $conf; $key = 'forum-alias-cache'; static $cache = array(); // 用静态变量只能在当前 request 生命周期缓存,跨进程需要再加一层缓存:redis/memcached/xcache/apc if (isset($cache[$key])) return $cache[$key]; if ('mysql' == $conf['cache']['type']) { $arr = well_forum_alias(); } else { $arr = cache_get($key); if (NULL === $arr) { $arr = well_forum_alias(); !empty($arr) AND cache_set($key, $arr); } } $cache[$key] = empty($arr) ? '' : $arr; return $cache[$key]; } ?>javascript - Difference between window.pageYOffset and document.body.getBoundingClientRect().top ? - Stack Overflow
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javascript - Difference between window.pageYOffset and document.body.getBoundingClientRect().top ? - Stack Overflow

programmeradmin6浏览0评论

I'm doing a progress bar depending on how much you scroll. Which of these two should I use?

function getScrollValue() {
    return ((parseInt(document.body.getBoundingClientRect().top) * -1));
}

or

function getScrollValue() {
    return window.pageYOffset;
}

I'm doing a progress bar depending on how much you scroll. Which of these two should I use?

function getScrollValue() {
    return ((parseInt(document.body.getBoundingClientRect().top) * -1));
}

or

function getScrollValue() {
    return window.pageYOffset;
}
Share Improve this question asked Dec 27, 2018 at 14:47 MCFreddie777MCFreddie777 1,2232 gold badges13 silver badges22 bronze badges 7
  • IntersectionObserver is probably the better solution for that. – str Commented Dec 27, 2018 at 14:56
  • 1 Use window.pageYOffset (IntersectionObserver is not supported by IE) – Jakob E Commented Dec 27, 2018 at 14:59
  • @JakobE There is a polyfill. – str Commented Dec 27, 2018 at 15:01
  • 1 Yep - but in this case (just monitoring page scroll) it's overkill (the polyfill also uses scroll listeners). I would use scroll listeners and passive events if available – Jakob E Commented Dec 27, 2018 at 15:09
  • @JakobE IntersectionObserver exists because the naive solution to scroll handlers often impose performance problems. It is not overkill to enhance performance for capable browsers while providing a polyfill for heavily outdated browsers. – str Commented Dec 27, 2018 at 15:12
 |  Show 2 more ments

2 Answers 2

Reset to default 5

Besides of window.pageYOffset being the more specialized API as well as a more performant solution for detecting the scrolling value, using getBoundingClientRect().top for attempting the same thing can have unexpected results if, for instance, the body has some margin-top that offsets its position.

EDIT

I've included the following jsPerf Test that shows a substantial difference of performance between the two alternatives, as well as how a third (older) API fares against them.

A simple example using the progress bar tag

/* test if passive events are supported */
var supportsPassive = false;
try { var opts = Object.defineProperty({}, 'passive', { get: function() { supportsPassive = true; }});
  window.addEventListener("testPassive", null, opts);
  window.removeEventListener("testPassive", null, opts);
} catch (e) {}

/* progress element */
const progress = document.querySelector('progress');

/* scroll listener */
addEventListener('scroll', e => {
    progress.value = pageYOffset/(document.body.clientHeight - innerHeight);
}, supportsPassive ? { passive: true } : false);
/* stretch and fix progress */ 
progress { width: 100%; position: fixed; }

/* add some scroll to the page */
body { margin: 0; height: 20000px; }
<progress value="0"></progress>

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