JSLint抱怨我的try / catch

问题描述

当通过运行的JavaScript对我而言，我不知道为什么。

The javascript, when run through JSLint yells at me and I am not sure why.

/*jslint browser: true, devel: true, evil: true, undef: true, nomen: true, eqeqeq: true, plusplus: true, bitwise: true, newcap: true, immed: true */

var foo = function() {
  try {
    console.log('foo');
  } catch(e) {
    alert(e);
  }

  try {
    console.log('bar');
  } catch(e) {
    alert(e);
  }
};

foo();

它告诉我：

} catch（e）{

似乎令人不安，我有一个第二个 catch（e）。为什么这是一个问题？它不是简单地将e设置为catch块内的局部变量？我需要为函数中的所有陷阱错误唯一地命名局部变量吗？

It appears to be upset that I have a second catch(e). Why would this be an issue? Does it not simply set e to local variable inside the catch block? Do I need to uniquely name the local variables for all trapped errors in a function?

推荐答案

对于JSLint， try..catch 具有将 e 声明为局部变量的隐含效果。因为在同一个函数中有两个这样的块（在JavaScript中没有块范围），所以JSLint看到声明已经被声明的变量。

To JSLint, try..catch has the implicit effect of declaring e as a local variable. Because you have two such blocks within the same function (there is no block scope in JavaScript), JSLint sees that as declaring a variable that has already been declared.

命名变量 e1 ， e2 ，等。来自JSLint的警告。这真的是一个问题吗？ ECMAScript 5规范第12.14节说：无论控制如何离开Block，LexicalEnvironment总是恢复到原来的状态。这实际上似乎是这样的：

Naming the variables e1, e2, etc. would prevent this warning from JSLint. Is it really a problem though? The ECMAScript 5 specification, section 12.14, says "No matter how control leaves the Block the LexicalEnvironment is always restored to its former state." This, in fact, does appear to be the case:

try {
    throw new Error("testing 1234");
} catch(fooBarBaz){
    alert("Catch: " + fooBarBaz);    // works
}

alert(fooBarBaz);    // throws exception

所以，总而言之，这只是JSLint的一个限制并且不太可能导致任何实际问题。

So, to conclude, this is simply a limitation of JSLint and is unlikely to lead to any practical problem.

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