Interesting: one ID selector can be killed for 256 class selectors.

By zhangxinxu from

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Address: http://www.zhangxinxu.com/wordpress? P = 2552

We should all know that the ID selector (#aaa{}) And class selector (.aaa{}) Is not an order of magnitude. The former is 1-0-0, while the latter is 0-1-0.
Therefore:

# ID {color: darkblue;}. Class {color: darkred;} <span id = "ID" class = "class"> what is the color? </Span>

The color is darkblue.

Interesting phenomenon

I suddenly remembered a video that I saw on my microblog: the video of a Japanese bee that surrounded and killed the bumblebee. Although beebot is a scum, there are enough numbers to make some interesting things-hot enough to beat thousands of bumblebees.

However, in the world of CSS, there is an interesting phenomenon like "winning by quantity. For example, here is an interesting story about how to beat an ID selector by 256 cascading class selectors.

The test code is as follows:

#id {  background: darkblue;}.c000.c001.c002.c003.c004.c005.c006.c007.c008.c009.c010.c011.c012.c013.c014.c015.c016.c017.c018.c019.c020.c021.c022.c023.c024.c025.c026.c027.c028.c029.c030.c031.c032.c033.c034.c035.c036.c037.c038.c039.c040.c041.c042.c043.c044.c045.c046.c047.c048.c049.c050.c051.c052.c053.c054.c055.c056.c057.c058.c059.c060.c061.c062.c063.c064.c065.c066.c067.c068.c069.c070.c071.c072.c073.c074.c075.c076.c077.c078.c079.c080.c081.c082.c083.c084.c085.c086.c087.c088.c089.c090.c091.c092.c093.c094.c095.c096.c097.c098.c099.c100.c101.c102.c103.c104.c105.c106.c107.c108.c109.c110.c111.c112.c113.c114.c115.c116.c117.c118.c119.c120.c121.c122.c123.c124.c125.c126.c127.c128.c129.c130.c131.c132.c133.c134.c135.c136.c137.c138.c139.c140.c141.c142.c143.c144.c145.c146.c147.c148.c149.c150.c151.c152.c153.c154.c155.c156.c157.c158.c159.c160.c161.c162.c163.c164.c165.c166.c167.c168.c169.c170.c171.c172.c173.c174.c175.c176.c177.c178.c179.c180.c181.c182.c183.c184.c185.c186.c187.c188.c189.c190.c191.c192.c193.c194.c195.c196.c197.c198.c199.c200.c201.c202.c203.c204.c205.c206.c207.c208.c209.c210.c211.c212.c213.c214.c215.c216.c217.c218.c219.c220.c221.c222.c223.c224.c225.c226.c227.c228.c229.c230.c231.c232.c233.c234.c235.c236.c237.c238.c239.c240.c241.c242.c243.c244.c245.c246.c247.c248.c249.c250.c251.c252.c253.c254.c255 {  background: darkred;}test {  display: block;  height: 100px;  width: 100px}

Then the HTML section:

<test id="id" class="c000 c001 c002 c003 c004 c005 c006 c007 c008 c009 c010 c011 c012 c013 c014 c015 c016 c017 c018 c019 c020 c021 c022 c023 c024 c025 c026 c027 c028 c029 c030 c031 c032 c033 c034 c035 c036 c037 c038 c039 c040 c041 c042 c043 c044 c045 c046 c047 c048 c049 c050 c051 c052 c053 c054 c055 c056 c057 c058 c059 c060 c061 c062 c063 c064 c065 c066 c067 c068 c069 c070 c071 c072 c073 c074 c075 c076 c077 c078 c079 c080 c081 c082 c083 c084 c085 c086 c087 c088 c089 c090 c091 c092 c093 c094 c095 c096 c097 c098 c099 c100 c101 c102 c103 c104 c105 c106 c107 c108 c109 c110 c111 c112 c113 c114 c115 c116 c117 c118 c119 c120 c121 c122 c123 c124 c125 c126 c127 c128 c129 c130 c131 c132 c133 c134 c135 c136 c137 c138 c139 c140 c141 c142 c143 c144 c145 c146 c147 c148 c149 c150 c151 c152 c153 c154 c155 c156 c157 c158 c159 c160 c161 c162 c163 c164 c165 c166 c167 c168 c169 c170 c171 c172 c173 c174 c175 c176 c177 c178 c179 c180 c181 c182 c183 c184 c185 c186 c187 c188 c189 c190 c191 c192 c193 c194 c195 c196 c197 c198 c199 c200 c201 c202 c203 c204 c205 c206 c207 c208 c209 c210 c211 c212 c213 c214 c215 c216 c217 c218 c219 c220 c221 c222 c223 c224 c225 c226 c227 c228 c229 c230 c231 c232 c233 c234 c235 c236 c237 c238 c239 c240 c241 c242 c243 c244 c245 c246 c247 c248 c249 c250 c251 c252 c253 c254 c255"></test>

As we often know, Id selection should be higher than Class. Therefore, the background color of the above element should be#idCorrespondingdarkblueDark blue. However, the above result is not dark blue,darkredDeep red.

Believe it? You can click here: 256 classes beat 1 ID demo page

Both IE, Mozilla, and WebKit browsers show the following results:

Interesting ~~

Other Instructions:
1. Because the test element does not exist, to be compatible with IE6 ~ 8. In the browser, you need to write an additional line of js code in the header:document.createElement("test");
2. Similarly, the weight of 256 consecutive nested labels is greater than that of one class.

Why?

It is said that by viewing the source code of the Firefox browser, all the class names (classes) are8-byte stringStored. Anyone who knows a little about bytes knows that the maximum value that 8 bytes can hold is 255. So when 256 classes appear at the same time, they will inevitably cross the edge and overflow to the ID area.

Gecko overflows the Count of classes into the count of IDS, each of which holds 8 bits.

-Cameron McCormack (@ heycam) August 16,201 2

Why is operabrowser different?

According to the information of an opera employee, operabrowser class names are stored16-byte string. Therefore, if the browser wants to overflow the class to the ID, it needs to have 65536 classes in a row. I don't know if it is because 16-byte strings affect the selector engine more than 8 ~~

Yes, opera uses 16 bits instead of 8. Bring on 65536 classes...

-Patrick H. lauke (@ patrick_h_lauke) August 16,201 2

Other benefits

Maybe many cssers are confused about the weight relationship before the selector. Nowadays, various css3 pseudo classes are like Valentine's Day gifts.

In order to save us from these hard-working page dolls, some people outside China have made a very easy-to-understand CSS selector type and weight relationship between them. The following is a 50% compressed image, which is easy to understand. Please add it to favorites ~~

Reference: http://cssn.in/ja/043

Original article, reproduced please indicate from Zhang xinxu-xin space-xin Sheng live [http://www.zhangxinxu.com]
Address: http://www.zhangxinxu.com/wordpress? P = 2552

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