In CSS selectors: the difference between class and ID selectors_html/css_WEB-ITnose

Same points: can be applied to any element

Differences:

1, ID selector only Can be used once in a document . Unlike class selectors, ID selectors can only be used once, and only once, in an HTML document. Class selectors can be used multiple times.

The following code is correct:

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41629fe13eda146adba1df631bc290d3China54bdf357c58b8a65c66d7c19c8e4d114 is a great country. . . . . 41629fe13eda146adba1df631bc290d3Xi Jinping54bdf357c58b8a65c66d7c19c8e4d114 is the current president of the country

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And the following code is wrong:

e388a4556c0f65e1904146cc1a846bee

c3f4d3105cf4ed5d7eba742a122e072eChina54bdf357c58b8a65c66d7c19c8e4d114 is a great country. . . . . c3f4d3105cf4ed5d7eba742a122e072eXi Jinping54bdf357c58b8a65c66d7c19c8e4d114 is the current President of the country

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2, You can use the class selector word list method to set multiple styles for an element at the same time. We can set multiple styles for one element at the same time, but this can only be achieved using class selectors, not ID selectors (ID word lists cannot be used).

The following code is correct (see the code editor on the right for the complete code)

.stress{    color:red;}.bigsize{    font-size:25px;}<p>到了<span <strong>class="stress bigsize"</strong>>三年级</span>下学期时，我们班上了一节公开课...</p>

The following code is incorrect (See the code editor on the right for the complete code)

#stressid{    color:red;}#bigsizeid{    font-size:25px;}<p>到了<span <strong>id="stressid bigsizeid"</strong>>三年级</span>下学期时，我们班上了一节公开课...</p>

e388a4556c0f65e1904146cc1a846beeArriveddb44137c18c84dee3ad665c8968e19b6Third graded6d448110e0324953b5d7bc1e2b276ceNext semester. (This is feasible)

Note: The above code can put color:red and font-size:25px; in a class selector. If you want to set a word It is much more convenient to set the color to red and set its font to 25px; but if a place only needs to set its color to red, then it is better to use a class selector, so the more detailed it is when writing a class selector. The better (I think)! ! !