blocks|key|1011294|text|您可以通过测试来查看错误是否确实是SyntaxError。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1011295|try+{
++++eval(code);+
}+catch+(e)+{
++++if+(e+instanceof+SyntaxError)+{
++++++++alert(e.message);
++++}
}|code-block|syntax|javascript|1011296|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|$]]

You can test to see if an error is indeed a SyntaxError.

<pre><code>try {
 eval(code); 
} catch (e) {
 if (e instanceof SyntaxError) {
 alert(e.message);
 }
}
</code></pre>

blocks|key|797044|text|您可以使用JsLint，它包含一个用javascript编写的javascript解析器。它将为你提供大量关于你的代码的信息，它可以被配置成更轻松或者更不轻松，等等。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|797045|entityMap|0|LINK|mutability|MUTABLE|url|http://www.jslint.com/^0|5|6|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

You can use <a href="http://www.jslint.com/" rel="nofollow noreferrer">JsLint</a> which contains a javascript parser written in javascript. It will give you lots of information about your code, it can be configured to be more relaxed or not, etc...

blocks|key|1011382|text|当使用try-catch来捕获特定类型的错误时，应该确保不会抑制其他类型的异常。否则，如果被评估的代码抛出一种不同类型的异常，它可能会消失，并导致代码的意外行为。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1011383|我建议写这样的代码：|1011384|try+{
++++eval(code);+
}+catch+(e)+{
++++if+(e+instanceof+SyntaxError)+{
++++++++alert(e.message);
++++}+else+{
++++++++throw+e;
++++}
}|code-block|syntax|javascript|1011385|请注意"else“部分。|1011386|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|N|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|O|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|P|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

When using try-catch for catching a particular type of error one should ensure that other types of exceptions are not suppressed. Otherwise if the evaluated code throws a different kind of exception it could disappear and cause unexpected behaviour of the code.

I would suggest writing code like this:

<pre><code>try {
 eval(code); 
} catch (e) {
 if (e instanceof SyntaxError) {
 alert(e.message);
 } else {
 throw e;
 }
}
</code></pre>

Please note the "else" section.

blocks|key|1011425|text|为了在验证后继续使用代码，我使用以下示例：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1011426|var+validCode+=+1;
try+{
++eval(+jsCode+);++++++++/*+Code+test+*/
}+catch+(e)+{
++if+(e+instanceof+SyntaxError)+{
++++validCode+=+0;
++++console.warn(e.message);
++}
}+finally+{
++if(validCode){
++++"do+some+magic"
++}
}|code-block|syntax|javascript|1011427|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|$]]

To continue using the code after validation, I use the following example:

<pre><code>var validCode = 1;
try {
 eval( jsCode ); /* Code test */
} catch (e) {
 if (e instanceof SyntaxError) {
 validCode = 0;
 console.warn(e.message);
 }
} finally {
 if(validCode){
 "do some magic"
 }
}
</code></pre>

blocks|key|797185|text|下面的代码是由go-oleg发布的，感谢他|type|unstyled|depth|inlineStyleRanges|entityRanges|data|797186|此代码验证正确的语法，否则返回错误|797187|注意:代码不是有效运行时错误，因为它使用ast解析器来分析正确的语法。|797188|要安装|797189|npm+install+esprima+--save|code-block|syntax|javascript|797190|代码：|797191|var+esprima+=+require('esprima');
var+userStringToTest+=+'var+a+=+50;';

var+isValid+=+isValidJs(userStringToTest);

if(isValid)+{
++alert('its+validated!');
}
else+{
++console.log('its+NOT+valid+syntax!');
}

function+isValidJs(testString)+{
++var+isValid+=+true;
++try+{
++++esprima.parse(testString);
++}
++catch(e)+{
++++isValid+=+false;
++}
++return+isValid;
}|797192|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|T|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|U|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|V|8|@]|9|@]|A|$]]|$1|H|3|I|5|J|7|W|8|@]|9|@]|A|$K|L]]|$1|M|3|N|5|6|7|X|8|@]|9|@]|A|$]]|$1|O|3|P|5|J|7|Y|8|@]|9|@]|A|$K|L]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

This Below code posted by go-oleg thanks to him
This code validate the correct syntax otherwise return error
Note:code is not vaildate run time error because it uses ast parser to analyze the correct syntax.
To Install
<pre><code>npm install esprima --save
</code></pre>
code:
<pre><code>var esprima = require('esprima');
var userStringToTest = 'var a = 50;';

var isValid = isValidJs(userStringToTest);

if(isValid) {
 alert('its validated!');
}
else {
 console.log('its NOT valid syntax!');
}

function isValidJs(testString) {
 var isValid = true;
 try {
 esprima.parse(testString);
 }
 catch(e) {
 isValid = false;
 }
 return isValid;
}
</code></pre>

I wanted to know if it is possible to find through javascript if a call to eval() has a syntax error or undefined variable, etc... so lets say I use eval for some arbitrary javascript is there a way to capture the error output of that eval?

eval javascript, check for syntax error

我想知道是否可以通过javascript发现eval()调用是否存在语法错误或未定义的变量等。假设我对一些任意的javascript使用eval，有没有一种方法可以捕获eval的错误输出？

问eval javascript，检查语法错误
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