blocks|key|3170573|text|$(".filter-icon")+-是一个jQuery函数调用。返回的值实际上不是数组，但它有一个length属性。函数调用结果的length是与选择器匹配的DOM中元素数的计数。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|BOLD|entityRanges|data|3170574|代码的目的是检查DOM中是否有任何元素具有类“过滤器-图标”。|3170575|在JavaScript编程中，遇到看起来似乎是数组但实际上并非如此的事情并不少见。令人高兴的是，许多针对实际数组的内置函数对于它们将接受的内容相当松散，因此您可以经常使用本机数组函数来对一些对象执行有趣的操作--假装是真正的数组。|3170576|entityMap^0|0|H|1E|6|1U|6|M|6|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]|$9|P|A|Q|B|C]|$9|R|A|S|B|C]|$9|T|A|U|B|D]]|E|@]|F|$]]|$1|G|3|H|5|6|7|V|8|@]|E|@]|F|$]]|$1|I|3|J|5|6|7|W|8|@]|E|@]|F|$]]|$1|K|3|-4|5|6|7|X|8|@]|E|@]|F|$]]]|L|$]]

This: <code>$(".filter-icon")</code> &mdash; is a jQuery function call. The returned value is in fact not an array, but it does have a <code>length</code> property. The <code>length</code> of the result of that function call is a count of the number of elements in the DOM that matched the selector.

The point of that code is to check whether there are any elements in a DOM that have the class "filter-icon".

It's not that uncommon in JavaScript programming to run into things that appear to be arrays, but which really aren't. Happily, many of the built-in functions for real arrays are fairly loose about what they'll accept, so you can quite often use native array functions to do interesting things with objects that just sort-of pretend to be real arrays.

blocks|key|3857762|text|if+($(".filter-icon").length+==+0)
++return;|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|3857763|这将检查具有类为filter-icon的所有元素。如果它找不到任何东西，它将返回计数器。|unstyled|offset|length|style|CODE|3857764|一个来自jquery网站的例子，用来计算no。divs：|3857765|$(+document.body+)
++.click(function()+{
++++$(+document.body+).append(+$(+"<div>"+)+);
++++var+n+=+$(+"div"+).length;
++++$(+"span"+).text(+"There+are+"+%2B+n+%2B+"+divs."+%2B
++++++"Click+to+add+more.");
++})|3857766|entityMap^0|0|8|B|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|R|8|@$G|S|H|T|I|J]]|9|@]|A|$]]|$1|K|3|L|5|F|7|U|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|V|8|@]|9|@]|A|$B|C]]|$1|O|3|-4|5|F|7|W|8|@]|9|@]|A|$]]]|P|$]]

<pre><code>if ($(".filter-icon").length == 0)
 return;
</code></pre>

This will check for all the elements which are having class as <code>filter-icon</code>. If it does not find any, it will return the counter.

An example from jquery website, to count the no. of divs : 

<pre><code>$( document.body )
 .click(function() {
 $( document.body ).append( $( "&lt;div&gt;" ) );
 var n = $( "div" ).length;
 $( "span" ).text( "There are " + n + " divs." +
 "Click to add more.");
 })
</code></pre>

blocks|key|3857828|text|所有四个答案都是正确的。$(“.filter-图标”)构造为JQuery，在DOM中搜索所有具有class=“filter-图标”属性的元素。它将返回0或多个元素，.length+==+0测试将确定是否有匹配项。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3857829|本质上说，|3857830|如果没有带有class=“过滤器-图标”的HTML标记，那么只需返回。|3857831|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|H|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|I|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|J|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|G|$]]

All four answers are correct. The $(".filter-icon") construct is JQuery, searching the DOM for all elements with a class="filter-icon" attribute. It will return 0 or more elements, and the .length == 0 test determines if there were no matches.

In essence, 

If there are no HTML tags with class="filter-icon", then simply return.

blocks|key|3857735|text|所以，$+is+jQuery。$()是一个函数调用，该函数返回一个jQuery对象，它的作用类似于一个数组。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3857736|如果代码如下所示，将更容易在操作中看到：|3857737|++++var+matches+=+$(".filter-icon");
++++if+(matches.length+==+0)
++++++++return;|code-block|syntax|javascript|3857738|$()函数的工作方式是从HTML页面中选择与css选择相匹配的元素，并将元素作为行为类似于数组的jQuery对象返回。|3857739|因为返回是一个数组，所以可以将其串为$(“..filter图标”).length，实际上这是编写它的更常见的方式。|3857740|即使您使用jQuery来选择一些仅在页面上出现一次的HTML元素，比如$("#myId")，它作为ID只在页面上出现一次，您仍然会得到一个可索引数组对象，它只会有一个项。|3857741|entityMap^0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|R|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|S|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|T|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|U|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|V|8|@]|9|@]|A|$]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

So, the $ is jQuery. The $() is a function call, and that function returns a jQuery object, which acts like an array.

It would be easier to see in action if the code looked like this:

<pre><code> var matches = $(".filter-icon");
 if (matches.length == 0)
 return;
</code></pre>

The way that the $() function works, is it selects elements from the HTML page that match the css selection, and returns the elements as a jQuery object that behaves like an array.

Since the return behaves as an array, you can string it together as $(".filter-icon").length, and in fact that is the more common way to write it.

Even if you use jQuery to select some HTML elements that only appear once on the page, such as $("#myId"), which, as an ID would only occur once on the page, you'll still get back an indexable array object, it just will have one item.

blocks|key|3857810|text|正如@Pointy所说，$是一个jQuery函数。但是，它返回一个数组，该数组具有属性length。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3857811|entityMap^0|C|1|17|6|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|M|8|@]|D|@]|E|$]]]|G|$]]

As said by @Pointy, <code>$</code> is a jQuery function. However, it returns an array, which has a property <code>length</code>.

I'm fairly new to JavaScript, and I'm not sure I fully understand what's going on with the code snippet below:

<pre><code>if ($(".filter-icon").length == 0)
 return;
</code></pre>

So I understand the <code>if</code> statement, but the part that I don't fully understand is the <code>$(".filter-icon").length</code>. After going through the documentation I'm a bit confused. How is <code>$(".filter-icon")</code> an array? I thought it was just anything that had a <code>filter-icon</code> class associated with it. How can you get the length of that?

I apologize for the basic question, but I'm very confused by this and it's hard to google with punctuation.

Understanding javascript arrays

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我对JavaScript相当陌生，我不太清楚下面的代码片段是怎么回事：if ($(".filter-icon").length == 0)  return;因此，我理解if语句，但我不完全理解的部分是$(".filter-icon").length。看完文档之后，我有点糊涂了。$(".filter-icon")是一个怎样的数组？我以为它只是一个与它相关的filter-icon类。你怎么能得到它的长

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