blocks|key|4168799|text|除非您真的有一个名为groups的全局变量(实际上这不是最好的想法)，否则您就是在与您的“局部”groups变量对话。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|4168800|由于EMCA-/Javascript确实具有函数作用域，并且您在那里使用的是闭包，因此您确实可以访问该变量。所以这里的问题不在于作用域。，，所以即使有一个具有完全相同名称的全局变量，所谓的词法作用域也会保证你可以访问你的局部变量。，，。|BOLD|4168801|实际问题是，return+groups在$.getJSON()完成之前就执行了。因为它创建了一个ajax请求，所以它是异步运行的。|4168802|您应该自己使用callback来处理数据：|4168803|function+get_groups(cb)+{
+++var+groups+=+[];

+++$.getJSON('get_groups.php',+function(response)+{
+++++++for+(var+i+in+response)+{
+++++++++++groups.push(response[i]);
+++++++}
+++++++cb.apply(null,+[groups]);
+++}
}

get_groups(function(groups){
+++//+do+something+with+groups+array
});|code-block|syntax|javascript|4168804|entityMap^0|A|6|1C|6|0|M|5|12|2|38|1|0|6|D|K|B|0|7|8|0|0^^$0|@$1|2|3|4|5|6|7|T|8|@$9|U|A|V|B|C]|$9|W|A|X|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Y|8|@$9|Z|A|10|B|H]|$9|11|A|12|B|H]|$9|13|A|14|B|H]]|D|@]|E|$]]|$1|I|3|J|5|6|7|15|8|@$9|16|A|17|B|C]|$9|18|A|19|B|C]]|D|@]|E|$]]|$1|K|3|L|5|6|7|1A|8|@$9|1B|A|1C|B|C]]|D|@]|E|$]]|$1|M|3|N|5|O|7|1D|8|@]|D|@]|E|$P|Q]]|$1|R|3|-4|5|6|7|1E|8|@]|D|@]|E|$]]]|S|$]]

Unless you really have a global variable with the name <code>groups</code> (which would be not the best idea actually), you are talking to your "local" <code>groups</code> variable.

Since EMCA-/Javascript does have function scope and you are using a closure there, you do have access to that variable. So the problem here, is not the scope.
So even with a global variable with the exact same name, the such called lexical scope will guarantee you the access to your local variable.

The actuall problem is, that <code>return groups</code> is executed before <code>$.getJSON()</code> does complete. Since it creates an ajax request, it run asynch.

You should use a <code>callback</code> yourself to process the data:

<pre><code>function get_groups(cb) {
 var groups = [];

 $.getJSON('get_groups.php', function(response) {
 for (var i in response) {
 groups.push(response[i]);
 }
 cb.apply(null, [groups]);
 }
}

get_groups(function(groups){
 // do something with groups array
});
</code></pre>

blocks|key|899072|text|这真的不是范围问题，而是$.getJSON()是异步的，这意味着这部分会在你返回后运行：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|899073|for+(var+i+in+response)+{
++groups.push(response[i]);
}|code-block|syntax|javascript|899074|您需要在异步请求的回调中调用需要此数据的任何函数，以便在数据可用时运行，如下所示：|899075|$.getJSON('get_groups.php',+function(response)+{
++++var+groups+=+[];
++++for+(var+i+in+response)+{
++++++++groups.push(response[i]);
++++}
++++doSomethingThatNeedsGroups(groups);
});|899076|当前正在填充您的组数组，但不是在需要的时候。如果您一定要返回它(我强烈建议按预期的方式使用异步模型)，您可以使用完整的$.ajax()版本并设置async:false。再说一次……如果可能的话，不要走这条路，只要数据可用，就坚持调用任何需要的函数，因为async:+false会锁定用户的浏览器。|899077|entityMap|0|LINK|mutability|MUTABLE|url|http://api.jquery.com/jQuery.getJSON/|1|http://api.jquery.com/jQuery.ajax/^0|C|B|C|B|0|0|0|0|0|1N|8|20|B|3I|C|1N|8|1|0^^$0|@$1|2|3|4|5|6|7|10|8|@$9|11|A|12|B|C]]|D|@$9|13|A|14|1|15]]|E|$]]|$1|F|3|G|5|H|7|16|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|17|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|18|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|19|8|@$9|1A|A|1B|B|C]|$9|1C|A|1D|B|C]|$9|1E|A|1F|B|C]]|D|@$9|1G|A|1H|1|1I]]|E|$]]|$1|Q|3|-4|5|6|7|1J|8|@]|D|@]|E|$]]]|R|$S|$5|T|U|V|E|$W|X]]|Y|$5|T|U|V|E|$W|Z]]]]

It's not a scope issue really, it's the fact that <a href="http://api.jquery.com/jQuery.getJSON/" rel="nofollow noreferrer"><code>$.getJSON()</code></a> is asynchronous, meaning that this part runs after you return:

<pre><code>for (var i in response) {
 groups.push(response[i]);
}
</code></pre>

You need to call whatever function needs this data in the callback of the asynchronous request, so it runs when the data's available, like this:

<pre><code>$.getJSON('get_groups.php', function(response) {
 var groups = [];
 for (var i in response) {
 groups.push(response[i]);
 }
 doSomethingThatNeedsGroups(groups);
});
</code></pre>

Currently you groups array is getting populated, just not when you need it to. If you absolutely have to return this (I strongly recommend using the asynchronous model the way it was intended) you can use the full <a href="http://api.jquery.com/jQuery.ajax/" rel="nofollow noreferrer"><code>$.ajax()</code></a> version and set <code>async:false</code>. Again...don't go that route if possible, stick to calling whatever function needs the data once it's available, as <code>async: false</code> will lock up the user's browser.

blocks|key|1641720|text|"$.getJSON('get_groups.php'，function(response)+{“是一个回调函数。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1641721|groups-Array中的更改会在回调和返回groups之后生效。|1641722|"get_groups"|1641723|trigger+callback|unordered-list-item|1641724|
|1641725|anynomous+|1641726|1641727|get_groups+end|1641728|1641729|请求url并注册callback|1641730|1641731|return+groups|1641732|1641733|end+of“get_groups”|1641734|1641735|trigger+callback|1641736|1641737|anynomous+callback-function+groups+of+anynomous|1641738|1641739|您不能直接返回回调函数的修改。|1641740|entityMap^0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|19|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|1A|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|1B|8|@]|9|@]|A|$]]|$1|F|3|G|5|H|7|1C|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|1D|8|@]|9|@]|A|$]]|$1|K|3|L|5|H|7|1E|8|@]|9|@]|A|$]]|$1|M|3|J|5|6|7|1F|8|@]|9|@]|A|$]]|$1|N|3|O|5|H|7|1G|8|@]|9|@]|A|$]]|$1|P|3|J|5|6|7|1H|8|@]|9|@]|A|$]]|$1|Q|3|R|5|H|7|1I|8|@]|9|@]|A|$]]|$1|S|3|J|5|6|7|1J|8|@]|9|@]|A|$]]|$1|T|3|U|5|H|7|1K|8|@]|9|@]|A|$]]|$1|V|3|J|5|6|7|1L|8|@]|9|@]|A|$]]|$1|W|3|X|5|H|7|1M|8|@]|9|@]|A|$]]|$1|Y|3|J|5|6|7|1N|8|@]|9|@]|A|$]]|$1|Z|3|10|5|H|7|1O|8|@]|9|@]|A|$]]|$1|11|3|J|5|6|7|1P|8|@]|9|@]|A|$]]|$1|12|3|13|5|H|7|1Q|8|@]|9|@]|A|$]]|$1|14|3|-4|5|6|7|1R|8|@]|9|@]|A|$]]|$1|15|3|16|5|6|7|1S|8|@]|9|@]|A|$]]|$1|17|3|-4|5|6|7|1T|8|@]|9|@]|A|$]]]|18|$]]

"$.getJSON('get_groups.php', function(response) {" is an Callback-Function.

The changes in the groups-Array are affect after the callback is trickerd and also after you return groups.

<ol>
<li>get_groups enterd</li>
<li>request the url and register a callback</li>
<li>return groups</li>
<li>end of "get_groups"</li>
<li>trigger callback</li>
<li>anynomous callback-function enterd</li>
<li>modifie groups-array</li>
<li>end of anynomous callback-function</li>
</ol>

you could not return the modifies of the callback-function directly.

I have the following Javascript function that should return an array of groups that are in database. It uses <code>$.getJSON()</code> method to call <code>get_groups.php</code> which actually reads from the database.

<pre><code>function get_groups() {
 var groups = [];

 $.getJSON('get_groups.php', function(response) {
 for (var i in response) {
 groups.push(response[i]);
 }
 }

 return groups;
}
</code></pre>

Unfortunately, this function does not work as expected because <code>groups.push(response[i]);
</code> does not fill the <code>var groups = [];</code> (as I understand it fills some other <code>groups</code> array, probably the global one).

Assuming that I don't want to have a global <code>groups</code> variable, how would you solve this problem ?

Need help with variable scope in Javascript

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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我有下面的Javascript函数，它应该返回数据库中的组的数组。它使用$.getJSON()方法调用get_groups.php，实际上是从数据库中读取数据。function get_groups() {    var groups = [];    $.getJSON('get_groups.php', funct...

问在Javascript中需要有关变量作用域的帮助
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