<span id="mktg5"></span>

<i id="mktg5"><meter id="mktg5"></meter></i>

        <label id="mktg5"><meter id="mktg5"></meter></label>
        最新文章專題視頻專題問答1問答10問答100問答1000問答2000關鍵字專題1關鍵字專題50關鍵字專題500關鍵字專題1500TAG最新視頻文章推薦1 推薦3 推薦5 推薦7 推薦9 推薦11 推薦13 推薦15 推薦17 推薦19 推薦21 推薦23 推薦25 推薦27 推薦29 推薦31 推薦33 推薦35 推薦37視頻文章20視頻文章30視頻文章40視頻文章50視頻文章60 視頻文章70視頻文章80視頻文章90視頻文章100視頻文章120視頻文章140 視頻2關鍵字專題關鍵字專題tag2tag3文章專題文章專題2文章索引1文章索引2文章索引3文章索引4文章索引5123456789101112131415文章專題3
        問答文章1 問答文章501 問答文章1001 問答文章1501 問答文章2001 問答文章2501 問答文章3001 問答文章3501 問答文章4001 問答文章4501 問答文章5001 問答文章5501 問答文章6001 問答文章6501 問答文章7001 問答文章7501 問答文章8001 問答文章8501 問答文章9001 問答文章9501
        當前位置: 首頁 - 科技 - 知識百科 - 正文

        CSS對Web頁面載入效率的影響分析總結_經驗交流

        來源:懂視網 責編:小采 時間:2020-11-27 18:55:25
        文檔

        CSS對Web頁面載入效率的影響分析總結_經驗交流

        CSS對Web頁面載入效率的影響分析總結_經驗交流:我們羅列了十幾條相關的知識與注意點,大家可以系統的探討一下,讓我們編寫的Web頁面打開更加流暢。 請不要告訴我,你看不懂E文,只是你不愿意看。 1、How the style system breaks up rules The style system breaks rules
        推薦度:
        導讀CSS對Web頁面載入效率的影響分析總結_經驗交流:我們羅列了十幾條相關的知識與注意點,大家可以系統的探討一下,讓我們編寫的Web頁面打開更加流暢。 請不要告訴我,你看不懂E文,只是你不愿意看。 1、How the style system breaks up rules The style system breaks rules

        我們羅列了十幾條相關的知識與注意點,大家可以系統的探討一下,讓我們編寫的Web頁面打開更加流暢。
          請不要告訴我,你看不懂E文,只是你不愿意看!!!

          1、How the style system breaks up rules
          The style system breaks rules up into four primary categories. It is critical to understand these categories, as they are the first line of defense as far as rule matching is concerned. I use the term key selector in the paragraphs that follow. The key selector is defined to be the rightmost occurrence of an id selector, a class selector, or a tag selector.

          1.1、ID Rules
          The first category consists of those rules that have an ID selector as their key selector.

        button#backButton { } /* This is an ID-categorized rule */
        #urlBar[type="autocomplete"] { } /* This is an ID-categorized rule */
        treeitem > treerow > treecell#myCell :active { } /* This is an ID-categorized rule */
          1.2、Class Rules
        If a rule has a class specified as its key selector, then it falls into this category.

        button.toolbarButton { } /* A class-based rule */
        .fancyText { } /* A class-based rule */
        menuitem > .menu-left[checked="true"] { } /* A class-based rule */
          1.3、Tag Rules
          If no class or ID is specified as the key selector, then the next potential category for a rule is the tag category. If a rule has a tag specified as its key selector, then the rule falls into this category.

        td { } /* A tag-based rule */
        treeitem > treerow { } /* A tag-based rule */
        input[type="checkbox"] { } /* A tag-based rule */
          1.4、Universal Rules
          All other rules fall into this category.


        :table { } /* A universal rule */
        [hidden="true"] { } /* A universal rule */
        * { } /* A universal rule */
        tree > [collapsed="true"] { } /* A universal rule */
          2、How the Style System Matches Rules
          The style system matches a rule by starting with the rightmost selector and moving to the left through the rule's selectors. As long as your little subtree continues to check out, the style system will continue moving to the left until it either matches the rule or bails out because of a mismatch.
          Your first line of defense is the rule filtering that occurs based on the type of the key selector. The purpose of this categorization is to filter out rules so that you don't even have to waste time trying to match them. This is the key to dramatically increasing performance. The fewer rules that you even have to check for a given element, the faster style resolution will be. As an example, if your element has an ID, then only ID rules that match your element's ID will be checked. Only class rules for a class found on your element will be checked. Only tag rules that match your tag will be checked. Universal rules will always be checked.

          3、Guidelines for Efficient CSS
          3.1、Avoid Universal Rules!
          Make sure a rule doesn't end up in the universal category!

          3.2、Don't qualify ID-categorized rules with tag names or classes
          If you have a style rule that has an ID selector as its key selector, don't bother also adding the tag name to the rule. IDs are unique, so you're slowing down the matching for no real reason.


        代碼如下:
        BAD - button#backButton { }
        BAD - .menu-left#newMenuIcon { }
        GOOD - #backButton { }
        GOOD - #newMenuIcon { }

          3.3、Don't qualify class-categorized rules with tag names
          Similar to the rule above, all of our classes will be unique. The convention you should use is to include the tag name in the class name.


        代碼如下:
        BAD - treecell.indented { }
        GOOD - .treecell-indented { }

          3.4、Try to put rules into the most specific category you can!
          The single biggest cause of slowdown in our system is that we have too many rules in the tag category. By adding classes to our elements, we can further subdivide these rules into class categories, and then we no longer waste time trying to match as many rules for a given tag.


        BAD - treeitem[mailfolder="true"] > treerow > treecell { }
        GOOD - .treecell-mailfolder { }
          3.5、Avoid the descendant selector!
          The descendant selector is the most expensive selector in CSS. It is dreadfully expensive, especially if a rule using the selector is in the tag or universal category. Frequently what is really desired is the child selector. The use of the descendant selector is banned in UI CSS without the explicit approval of your skin's module owner.

        BAD - treehead treerow treecell { }
        BETTER, BUT STILL BAD (see next guideline) - treehead > treerow > treecell { }
          3.6、Tag-categorized rules should never contain a child selector!
          Avoid using the child selector with tag-categorized rules. You will dramatically increase the matching time (especially if the rule is likely to be matched more often than not) for all occurrences of that element.


        BAD - treehead > treerow > treecell { }
        BEST - .treecell-header { }
          3.7、Question all usages of the child selector!
          Be careful about using the child selector. If you can come up with a way to avoid having to use it, do so. In particular, the child selector is frequently used with RDF trees and menus like so.


        BAD - treeitem[IsImapServer="true"] > treerow > .tree-folderpane-icon { }
          Remember that attributes from RDF can be duplicated in a template! Take advantage of this fact to duplicate RDF properties on child XUL elements that wish to change based off that attribute.


        GOOD - .tree-folderpane-icon[IsImapServer="true"] { }
          3.8、Rely on inheritance!
          Learn which properties inherit, and allow them to do so! We have explicitly set up XUL widgetry so that you can put list-style-image (just one example) or font rules on the parent tag, and it will filter in to the anonymous content. You don't have to waste time writing a rule that talks directly to the anonymous content.


        BAD - #bookmarkMenuItem > .menu-left { list-style-image: url(blah); }
        GOOD - #bookmarkMenuItem { list-style-image: url(blah); }
          In the above example, the desire to style the anonymous content (without understanding that list-style-image inherits) resulted in a rule that was in the class category, when this rule really should have ended up being in the most specific category of all, the ID category.
          Remember, especially with anonymous content, that they all have the same classes! The bad rule above causes the icon of every menu to be checked to see if it is contained in the bookmarks menu item. This is hideously expensive (since there are many menus); this rule never should have even been checked by any menu other than the bookmarks menu.

          3.9、Use -moz-image-region!
          Putting a bunch of images into a single image file and selecting them with -moz-image-region performs significantly better than putting each image into its own file.
          Original Document Information - Author: David Hyatt

        聲明:本網頁內容旨在傳播知識,若有侵權等問題請及時與本網聯系,我們將在第一時間刪除處理。TEL:177 7030 7066 E-MAIL:11247931@qq.com

        文檔

        CSS對Web頁面載入效率的影響分析總結_經驗交流

        CSS對Web頁面載入效率的影響分析總結_經驗交流:我們羅列了十幾條相關的知識與注意點,大家可以系統的探討一下,讓我們編寫的Web頁面打開更加流暢。 請不要告訴我,你看不懂E文,只是你不愿意看。 1、How the style system breaks up rules The style system breaks rules
        推薦度:
        標簽: 效率 頁面 分析
        • 熱門焦點

        最新推薦

        猜你喜歡

        熱門推薦

        專題
        Top
        主站蜘蛛池模板: 久久久久亚洲Av片无码v| 久久久亚洲精品蜜桃臀| 亚洲成人网在线播放| 午夜无码A级毛片免费视频| 亚洲热妇无码AV在线播放| 久久最新免费视频| 日韩亚洲变态另类中文| 国产真人无码作爱免费视频| 国产亚洲综合网曝门系列| 大地资源中文在线观看免费版| 亚洲精品乱码久久久久久中文字幕| a级在线免费观看| 亚洲男人第一av网站| 亚洲人成无码久久电影网站| 狠狠热精品免费观看| 久久久久亚洲AV综合波多野结衣 | 中国黄色免费网站| 亚洲色偷偷偷鲁综合| 亚洲免费精彩视频在线观看| 亚洲国产成人资源在线软件| 成年性羞羞视频免费观看无限| 狼人大香伊蕉国产WWW亚洲| 国产成人亚洲综合无码| 一区二区三区在线免费看 | 亚洲精品无码mⅴ在线观看| 午夜成年女人毛片免费观看| 男人和女人高潮免费网站| 亚洲国产一二三精品无码| 成人免费黄色网址| 亚洲日韩中文字幕在线播放| 香蕉成人免费看片视频app下载| 亚洲已满18点击进入在线观看| 中文字幕成人免费高清在线视频| 亚洲av无码不卡一区二区三区| 99久久久国产精品免费无卡顿 | 一区二区无码免费视频网站| 老司机午夜在线视频免费| 亚洲处破女AV日韩精品| 成人片黄网站A毛片免费| a一级毛片免费高清在线| 亚洲一区二区三区久久|