blocks|key|2248623|text|假设您不能影响您正在使用的JSON，那么您检查的方式几乎是唯一的方法。尽管我更喜欢检查!==+undefined。这纯粹是我的编程习惯，因为我不喜欢用if+(object)检查object的有效性。我总是将这一行等同于if(object+===+true)，从布尔逻辑的角度来看，这并不是一回事。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2248624|if+(+data.foo+!==+undefined+&&+data.foo.bar+!==+undefined+&&+data.foo.bar.baz+!==+undefined)+{+}|code-block|syntax|javascript|2248625|你也许可以不检查data.foo+!==+undefined，因为你说foo可能是一个空对象。|2248626|如果您的代码有很多这样的检查，您可以在收到JSON数据时预先进行一次检查，并填充任何缺少的对象：|2248627|if+(+data.foo+===+undefined)+data.foo+=+{};
if+(+data.foo.bar+===+undefined)+data.foo.bar+=+{};
if+(+data.foo.bar.baz+===+undefined)+data.foo.bar.baz+=+null;++//+or+skip+this,+I+suppose...|2248628|entityMap^0|17|D|23|B|2G|6|31|J|0|0|8|M|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]|$9|V|A|W|B|C]|$9|X|A|Y|B|C]|$9|Z|A|10|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|11|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|12|8|@$9|13|A|14|B|C]]|D|@]|E|$]]|$1|M|3|N|5|6|7|15|8|@]|D|@]|E|$]]|$1|O|3|P|5|H|7|16|8|@]|D|@]|E|$I|J]]|$1|Q|3|-4|5|6|7|17|8|@]|D|@]|E|$]]]|R|$]]

Assuming you can't affect the JSON that you are consuming, the way you are checking is pretty much the only way of doing this. Although I prefer checking for <code>!== undefined</code>. This is purely a programming idiosyncrasy I have, since I don't like thinking of <code>if (object)</code> checking for the validity of <code>object</code>. I always equate that line with <code>if(object === true)</code>, which isn't really the same thing from a boolean logic perspective.

<pre><code>if ( data.foo !== undefined &amp;&amp; data.foo.bar !== undefined &amp;&amp; data.foo.bar.baz !== undefined) { }
</code></pre>

You might be able to get away with not checking <code>data.foo !== undefined</code>, since you said foo could be an empty object.

If your code would have a lot of these checks, you could do one check up front when the JSON data is received and fill in any missing objects:

<pre><code>if ( data.foo === undefined) data.foo = {};
if ( data.foo.bar === undefined) data.foo.bar = {};
if ( data.foo.bar.baz === undefined) data.foo.bar.baz = null; // or skip this, I suppose...
</code></pre>

blocks|key|888983|text|如果您试图捕获深度嵌套对象上所有可能的错误，那么您可以使用多个if条件：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|888984|+if+(data+&&+data.foo+&&+data.foo.bar+&&+data.foo.bar.baz+)+{+}|code-block|syntax|javascript|888985|或者，如果失败不是预期的情况，您可以使用异常处理程序：|888986|try+{
++++var+item+=+data.foo.bar.baz;
++++//+operate+on+item
}+catch(e)+{
++++//+perform+any+actions+when+it+failed
}|888987|有时，使用单个异常处理程序保护代码块可以极大地简化错误处理。当异常触发时，异常的性能比if测试差，所以您应该记住这一点，但意外的失败通常是异常最擅长的处理方式，有时它们可以真正简化您的其余代码。|888988|似乎有一些开发人员基本上从来不想编写异常代码，而是更喜欢使用大量的if测试，但他们存在于语言中，因为他们非常擅长帮助解决某些类型的问题。|888989|entityMap^0|V|2|0|0|0|0|17|2|0|X|2|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|X|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|Y|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|Z|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|10|8|@$9|11|A|12|B|C]]|D|@]|E|$]]|$1|Q|3|R|5|6|7|13|8|@$9|14|A|15|B|C]]|D|@]|E|$]]|$1|S|3|-4|5|6|7|16|8|@]|D|@]|E|$]]]|T|$]]

If you're trying to catch all possible errors on a deeply nested object, then you can either use the multiple <code>if</code> conditions:

<pre><code> if (data &amp;&amp; data.foo &amp;&amp; data.foo.bar &amp;&amp; data.foo.bar.baz ) { }
</code></pre>

Or, if failure is not an expected condition, you can use an exception handler:

<pre><code>try {
 var item = data.foo.bar.baz;
 // operate on item
} catch(e) {
 // perform any actions when it failed
}
</code></pre>

There are times when protecting a block of code with a single exception handler can vastly simplify your error handling. Exceptions perform worse than <code>if</code> tests when the exception fires so you should keep that in mind, but unexpected failures is often what exceptions are best at handling and they can sometimes really simplify the rest of your code.

There seem to be some developers that basically never want to code with exceptions, preferring to use lots of <code>if</code> tests instead, but they are there in the language because they are very good at helping with some types of problems.

blocks|key|885786|text|丑陋、令人讨厌、可怕的方式是使用eval或try..catch。更健壮的方法是使用typeof|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|885787|if+(typeof+foo+!=+'undefined'+&&+foo+!==+Null+&&
+++typeof+foo.bar+!=+'undefined'+&&+foo.bar+!==+Null+&&+
+++...+
)+{
++++//+stuff
}|code-block|syntax|javascript|885788|然而，只有当最终属性的值不是undefined时，它才能工作(即，当属性存在但具有未定义的值时，它将失败)。|885789|您可以创建一个更精确的通用属性测试器来测试自己的属性：|885790|function+testChain(obj)+{

++++for+(var+i=1,+iLen=arguments.length;+i<iLen;+i%2B%2B)+{

++++++++if+(obj.hasOwnProperty(arguments[i]))+{
++++++++++obj+=+obj[arguments[i]];

++++++++}+else+{
++++++++++return+false;
++++++++}
++++}
++++return+true;
}

alert(+testChain({a:{b:'b'}},+'a',+'b')+);+//+true|885791|但这不会检查继承的属性。要检查这些属性，可以使用propertyIsEnumerable，但这不会检查不可枚举的属性(例如，内置对象的本机方法)。|885792|因此，实际上没有通用的解决方案，您只能针对特定情况量身定做一个。|885793|entityMap^0|G|4|L|A|15|6|0|0|E|9|0|0|0|O|K|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@$9|X|A|Y|B|C]|$9|Z|A|10|B|C]|$9|11|A|12|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|13|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|14|8|@$9|15|A|16|B|C]]|D|@]|E|$]]|$1|M|3|N|5|6|7|17|8|@]|D|@]|E|$]]|$1|O|3|P|5|H|7|18|8|@]|D|@]|E|$I|J]]|$1|Q|3|R|5|6|7|19|8|@$9|1A|A|1B|B|C]]|D|@]|E|$]]|$1|S|3|T|5|6|7|1C|8|@]|D|@]|E|$]]|$1|U|3|-4|5|6|7|1D|8|@]|D|@]|E|$]]]|V|$]]

The ugly, nasty, horrible way is to use either <code>eval</code> or <code>try..catch</code>. A more robust way is to use <code>typeof</code>:

<pre><code>if (typeof foo != 'undefined' &amp;&amp; foo !== Null &amp;&amp;
 typeof foo.bar != 'undefined' &amp;&amp; foo.bar !== Null &amp;&amp; 
 ... 
) {
 // stuff
}
</code></pre>

However that only works if the final property has a value other than <code>undefined</code> (i.e. it will fail where the property exists but has the undefined value).

You can create a more accurate generic property tester to test for own properties:

<pre><code>function testChain(obj) {

 for (var i=1, iLen=arguments.length; i&lt;iLen; i++) {

 if (obj.hasOwnProperty(arguments[i])) {
 obj = obj[arguments[i]];

 } else {
 return false;
 }
 }
 return true;
}

alert( testChain({a:{b:'b'}}, 'a', 'b') ); // true
</code></pre>

but that won't check inherited properties. To check for those, you can use <code>propertyIsEnumerable</code>, but that won't check non–enumerable properties (e.g. native methods of built–in objects).

So there really is no generic solution, you can only tailor one for a specific case.

I might receive a JSON structure like this

<pre><code>foo: {}
</code></pre>

Or I might like this:

<pre><code>foo: {bar: {baz: 1} }
</code></pre>

When I check the first data structure for existence like this:

<pre><code>if ( data.foo.bar.baz ) { }
</code></pre>

The script stops running altogether. I can't see any javascript errors on the browser or anything. It just stops. Either way tho, it would be nice to be able to do the above instead of:

<pre><code>if ( data.foo &amp;&amp; data.foo.bar &amp;&amp; data.foo.bar.baz ) { }
</code></pre>

What's the best way to address this issue?

Javascript object of unknown arbitrary depth causes script to stop execution

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。

文章

问答

视频

学习中心

腾讯云实验室

直播

竞赛

腾讯云代码分析专区

腾讯iOA零信任安全管理系统专区

腾讯云架构师技术同盟交流圈

腾讯云数据库专区

腾讯云顾问专区

腾讯云原生专区

腾讯混元专区

腾讯云TCE专区

腾讯云Lighthouse专区

腾讯云HAI专区

腾讯云Edgeone专区

腾讯云存储专区

腾讯云智能专区

腾讯轻联专区 

腾讯云开发专区

TAPD专区

腾讯轻量云游戏服专区

腾讯云最具价值专家

腾讯云架构师技术同盟

腾讯云创作之星

腾讯云开发者先锋

腾讯云代码助手

云原生构建

TAPD 敏捷项目管理

Cloud Studio

SDK中心

API中心

命令行工具

涵盖代码开发、场景应用、自动测试全流程，助你从零构建专属AI助手

一站式MCP教程库，解锁AI应用新玩法

我可能会收到这样的JSON结构foo: {}或者我可能会喜欢这样：foo: {bar: {baz: 1} }当我像这样检查第一个数据结构是否存在时：if ( data.foo.bar.baz ) { }脚本将完全停止运行。我在浏览器上看不到任何javascript错误。它就会停下来。不管怎样，最好能做到以上几点，而不是...

问未知任意深度的Javascript对象导致脚本停止执行
EN

Stack Overflow用户

社区

活动

圈层

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问未知任意深度的Javascript对象导致脚本停止执行EN