blocks|key|933647|text|它不会捕获示例中的任何内容的原因是，一旦调用了geocode()回调，try/catch块就结束了。因此，geocode()回调是在try块的作用域之外执行的，因此不能被它捕获。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|933648|据我所知，在JavaScript回调中捕获抛出的异常是不可能的(至少，不可能以任何简单的方式)。|933649|entityMap^0|N|9|Z|9|1H|9|1U|3|0|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]|$9|M|A|N|B|C]|$9|O|A|P|B|C]|$9|Q|A|R|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|S|8|@]|D|@]|E|$]]|$1|H|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|I|$]]

The reason it won't catch anything in your example is because once the <code>geocode()</code> callback is called, the <code>try/catch</code> block is over. Therefore the <code>geocode()</code> callback is executed outside the scope of the <code>try</code> block and thus not catchable by it. 

As far as I know, it is not possible to catch exceptions thrown in JavaScript callbacks (at least, not in any straightforward manner).

blocks|key|1148208|text|您确实可以捕获在JavaScript回调函数中触发的异常。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1148209|关键是在回调代码中设置try/catch块，因为回调代码外部的任何try/catch块在回调代码执行时都已经退出。因此，虽然上面的try/catch块不能捕获调用回调函数时抛出的任何异常，但您仍然可以这样做：|offset|length|style|CODE|1148210|//+this+will+cause+an+exception+ing+google.maps.Geocoder().geocode()+
//+since+it+expects+a+string.
var+zipcode+=+30045;+
var+map+=+new+google.maps.Map(document.getElementById('map_canvas'),+{
++++zoom:+5,
++++center:+new+google.maps.LatLng(35.137879,+-82.836914),
++++mapTypeId:+google.maps.MapTypeId.ROADMAP
});
//+exception+in+callback:
var+geo+=+new+google.maps.Geocoder().geocode({+'address':+zipcode+},+
+++function(geoResult,+geoStatus)+{
++++++try+{
++++++++++if+(geoStatus+!=+google.maps.GeocoderStatus.OK)+console.log(geoStatus);
++++++}+catch(e){
++++++++++alert("Callback+Exception+caught!");
++++++}
+++}
);|code-block|syntax|javascript|1148211|当抛出异常时，您将能够捕获该异常。我不能百分之百确定是否会出现这种情况，所以我写了一些测试代码来验证。在Chrome+19.0.1055.1开发版本中，该异常被捕获。|1148212|entityMap^0|0|B|9|X|9|1T|9|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|R|8|@$D|S|E|T|F|G]|$D|U|E|V|F|G]|$D|W|E|X|F|G]]|9|@]|A|$]]|$1|H|3|I|5|J|7|Y|8|@]|9|@]|A|$K|L]]|$1|M|3|N|5|6|7|Z|8|@]|9|@]|A|$]]|$1|O|3|-4|5|6|7|10|8|@]|9|@]|A|$]]]|P|$]]

You can indeed catch exceptions that fire within a JavaScript callback function.

The key is to set up the <code>try/catch</code> block within the callback code, as any <code>try/catch</code> blocks outside the callback code will have already exited by the time the callback code is executed. So while your <code>try/catch</code> block above won't be able to catch any exceptions that get thrown when the callback function is called, you can still do something like this:

<pre><code>// this will cause an exception ing google.maps.Geocoder().geocode() 
// since it expects a string.
var zipcode = 30045; 
var map = new google.maps.Map(document.getElementById('map_canvas'), {
 zoom: 5,
 center: new google.maps.LatLng(35.137879, -82.836914),
 mapTypeId: google.maps.MapTypeId.ROADMAP
});
// exception in callback:
var geo = new google.maps.Geocoder().geocode({ 'address': zipcode }, 
 function(geoResult, geoStatus) {
 try {
 if (geoStatus != google.maps.GeocoderStatus.OK) console.log(geoStatus);
 } catch(e){
 alert("Callback Exception caught!");
 }
 }
);
</code></pre>

and you'll be able to capture the exception when it is thrown. I wasn't 100% sure whether that would be the case or not, so I wrote some test code to verify. The exception is captured as expected on Chrome 19.0.1055.1 dev.

blocks|key|933837|text|可以，您可以覆盖window.onerror的默认行为|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|933838|window.onerror+=+function(message,+file,+lineNumber)+{
++//+all+errors+will+be+caught+here
++//+you+can+use+`message`+to+make+sure+it's+the+error+you're+looking+for
++//+returning+true+overrides+the+default+window+behaviour
++return+true;+
};|code-block|syntax|javascript|933839|entityMap|0|LINK|mutability|MUTABLE|url|https://developer.mozilla.org/en/DOM/window.onerror^0|8|E|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

Yes, you can override the default behaviour of <a href="https://developer.mozilla.org/en/DOM/window.onerror" rel="noreferrer">window.onerror</a>:

<pre><code>window.onerror = function(message, file, lineNumber) {
 // all errors will be caught here
 // you can use `message` to make sure it's the error you're looking for
 // returning true overrides the default window behaviour
 return true; 
};
</code></pre>

blocks|key|1148303|text|我已经通过猴子修补控制台日志检测到了这个错误。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1148304|if(window.console+&&+console.error){
++++var+old+=+console.error;
++++console.error+=+function(){
++++++++if(arguments[0].indexOf('Google+Maps+API+error')!=-1){
++++++++++++alert('Bad+Google+API+Key+'%2B+arguments[0]);
++++++++}
++++++++Array.prototype.unshift.call(arguments);

++++++++old.apply(this,+arguments);
++++}
}|code-block|syntax|javascript|1148305|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

I have detected the error by monkey patching the console logs.

<pre><code>if(window.console &amp;&amp; console.error){
 var old = console.error;
 console.error = function(){
 if(arguments[0].indexOf('Google Maps API error')!=-1){
 alert('Bad Google API Key '+ arguments[0]);
 }
 Array.prototype.unshift.call(arguments);

 old.apply(this, arguments);
 }
}
</code></pre>

blocks|key|1148326|text|以下是我的方法：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1148327|//+the+purpose+of+this+wrapper+is+to+ensure+that+any
//+uncaught+exceptions+after+a+setTimeout+still+get+caught
function+callbackWrapper(func)+{
++++return+function()+{
++++++++try+{
++++++++++++func();
++++++++}+catch+(err)+{
++++++++++++//+callback+will+reach+here+:)
++++++++++++//+do+appropriate+error+handling
++++++++++++console.log("error");
++++++++}
++++}
}

try+{
++++setTimeout(callbackWrapper(function()+{throw+"ERROR";}),+1000);
}+catch+(err)+{
++++//+callback+will+never+reach+here+:(
}|code-block|syntax|javascript|1148328|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Here's my approach:

<pre><code>// the purpose of this wrapper is to ensure that any
// uncaught exceptions after a setTimeout still get caught
function callbackWrapper(func) {
 return function() {
 try {
 func();
 } catch (err) {
 // callback will reach here :)
 // do appropriate error handling
 console.log("error");
 }
 }
}

try {
 setTimeout(callbackWrapper(function() {throw "ERROR";}), 1000);
} catch (err) {
 // callback will never reach here :(
}
</code></pre>

blocks|key|1148392|text|根据所有答案，try/catch+%2B+callback是在不同的上下文中设置的，但是--您如何解释此代码try/catch的工作原理？|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1148393|function+doSomeAsynchronousOperation(cb)+{
++cb(3);
}

function+myApiFunc()+{
++/*
+++*+This+pattern+does+NOT+work!
+++*/
++try+{
++++doSomeAsynchronousOperation((err)+=>+{
++++++if+(err)+{
++++++++console.log('got+here');
++++++++throw+err;
++++++}

++++});
++}+catch+(ex)+{
++++console.log(ex);
++}
}

myApiFunc();|code-block|syntax|javascript|1148394|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

According to all answers, try/catch + callback is set on a different context but then - how would you explain this code try/catch working?

<pre><code>function doSomeAsynchronousOperation(cb) {
 cb(3);
}

function myApiFunc() {
 /*
 * This pattern does NOT work!
 */
 try {
 doSomeAsynchronousOperation((err) =&gt; {
 if (err) {
 console.log('got here');
 throw err;
 }

 });
 } catch (ex) {
 console.log(ex);
 }
}

myApiFunc();
</code></pre>

blocks|key|1148446|text|如果您可以使用Promises和async/await，则可以按照以下示例代码进行解决：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1148447|async+function+geocode(zipcode)+{

++return+new+Promise((resolve,+reject)+=>+{

++++const+g+=+new+google.maps.Geocoder().geocode({+'address':+zipcode+},++function(geoResult,+geoStatus)+{
++++++if+(geoStatus+!=+google.maps.GeocoderStatus.OK)+{
++++++++reject(new+Error("Callback+Exception+caught"));
++++++}+else+{
++++++++resolve(g);
++++++};

++++});
++});
}

try+{
++//+...

++//+g+will+be+an+instance+of+new+google.maps.Geocoder().geocode..
++//+you+can+resolve+with+desired+variables
++const+g+=+await+geocode(zipcode);

++//+...
}+catch(+e+)+{
++console.log(e);
}|code-block|syntax|javascript|1148448|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

If you can use Promises and async/await, it can be solved as shown in sample code below:

<pre><code>async function geocode(zipcode) {

 return new Promise((resolve, reject) =&gt; {

 const g = new google.maps.Geocoder().geocode({ 'address': zipcode }, function(geoResult, geoStatus) {
 if (geoStatus != google.maps.GeocoderStatus.OK) {
 reject(new Error("Callback Exception caught"));
 } else {
 resolve(g);
 };

 });
 });
}

try {
 // ...

 // g will be an instance of new google.maps.Geocoder().geocode..
 // you can resolve with desired variables
 const g = await geocode(zipcode);

 // ...
} catch( e ) {
 console.log(e);
}
</code></pre>

Is there a way to catch exceptions in JavaScript callbacks? Is it even possible?

<pre><code>Uncaught Error: Invalid value for property &lt;address&gt;
</code></pre>

Here is the jsfiddle: <a href="http://jsfiddle.net/kjy112/yQhhy/" rel="noreferrer">http://jsfiddle.net/kjy112/yQhhy/</a>

<pre><code>try {
 // this will cause an exception in google.maps.Geocoder().geocode() 
 // since it expects a string.
 var zipcode = 30045; 
 var map = new google.maps.Map(document.getElementById('map_canvas'), {
 zoom: 5,
 center: new google.maps.LatLng(35.137879, -82.836914),
 mapTypeId: google.maps.MapTypeId.ROADMAP
 });
 // exception in callback:
 var geo = new google.maps.Geocoder().geocode({ 'address': zipcode }, 
 function(geoResult, geoStatus) {
 if (geoStatus != google.maps.GeocoderStatus.OK) console.log(geoStatus);
 }
 );
} catch (e) {
 if(e instanceof TypeError)
 alert('TypeError');
 else
 alert(e);
}​
</code></pre>

Is it possible to catch exceptions thrown in a JavaScript async callback?

有没有办法在JavaScript回调中捕获异常？这有可能吗？Uncaught Error: Invalid value for property <address>这是jsfiddle：try { // this will cause an exception in google.maps.Geocoder()....

问可以捕获JavaScript异步回调中抛出的异常吗？
EN

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问可以捕获JavaScript异步回调中抛出的异常吗？EN

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问可以捕获JavaScript异步回调中抛出的异常吗？
EN