我想在我的JS代码中抛出一些东西,我想让它们成为instanceof Error,但我也想让它们成为其他东西。
在Python中,通常会子类化Exception。
在JS中应该做什么?
我想在我的JS代码中抛出一些东西,我想让它们成为instanceof Error,但我也想让它们成为其他东西。
在Python中,通常会子类化Exception。
在JS中应该做什么?
当前回答
编辑:请阅读评论。我的目的是提供一个跨浏览器的解决方案,它可以在所有浏览器中工作,并在支持的地方提供堆栈跟踪。
编辑:我创建这个社区维基是为了允许更多的编辑。
V8 (Chrome / Node.JS)的解决方案,在Firefox中工作,并可以修改为在IE中正常工作。(见文末)
function UserError(message) {
this.constructor.prototype.__proto__ = Error.prototype // Make this an instanceof Error.
Error.call(this) // Does not seem necessary. Perhaps remove this line?
Error.captureStackTrace(this, this.constructor) // Creates the this.stack getter
this.name = this.constructor.name; // Used to cause messages like "UserError: message" instead of the default "Error: message"
this.message = message; // Used to set the message
}
“让我看看代码!”
短版:
function UserError(message) {
this.constructor.prototype.__proto__ = Error.prototype
Error.captureStackTrace(this, this.constructor)
this.name = this.constructor.name
this.message = message
}
我保留这个。构造器。原型。__proto__ =错误。函数中的原型将所有代码保存在一起。但是你也可以替换这个。使用UserError构造函数,这允许你将代码移到函数之外,所以它只被调用一次。
如果您走那条路,请确保在第一次抛出UserError之前调用该行。
这个警告并不适用于函数,因为函数是先创建的,不管顺序如何。因此,您可以将函数移动到文件的末尾,没有任何问题。
浏览器兼容性
工作在Firefox和Chrome(和Node.JS),并满足所有承诺。
ie浏览器出现如下问题
Errors do not have err.stack to begin with, so "it's not my fault". Error.captureStackTrace(this, this.constructor) does not exist so you need to do something else like if(Error.captureStackTrace) // AKA if not IE Error.captureStackTrace(this, this.constructor) toString ceases to exist when you subclass Error. So you also need to add. else this.toString = function () { return this.name + ': ' + this.message } IE will not consider UserError to be an instanceof Error unless you run the following some time before you throw UserError UserError.prototype = Error.prototype
其他回答
Crescent Fresh的答案是误导性的。尽管他的警告是无效的,但还有其他一些限制他没有提到。
首先,Crescent的“警告:”段落中的推理没有意义。这种解释意味着,与多个catch语句相比,编码“一堆if (error instanceof MyError) else…”在某种程度上是累赘或冗长的。单个catch块中的多个instanceof语句与多个catch语句一样简洁——干净简洁的代码,没有任何技巧。这是模拟Java出色的特定于可抛出子类型的错误处理的好方法。
WRT“显示子类的消息属性没有得到设置”,如果使用正确构造的Error子类,则不会出现这种情况。要创建自己的ErrorX Error子类,只需复制以"var MyError ="开头的代码块,将"MyError"改为"ErrorX"。(如果您想向子类添加自定义方法,请遵循示例文本)。
The real and significant limitation of JavaScript error subclassing is that for JavaScript implementations or debuggers that track and report on stack trace and location-of-instantiation, like FireFox, a location in your own Error subclass implementation will be recorded as the instantiation point of the class, whereas if you used a direct Error, it would be the location where you ran "new Error(...)"). IE users would probably never notice, but users of Fire Bug on FF will see useless file name and line number values reported alongside these Errors, and will have to drill down on the stack trace to element #1 to find the real instantiation location.
我的解决方案比其他提供的答案更简单,也没有缺点。
它保留了Error原型链和Error上的所有属性,而不需要对它们有具体的了解。它已经在Chrome, Firefox, Node和IE11中进行了测试。
唯一的限制是在调用堆栈的顶部有一个额外的条目。但这很容易被忽视。
下面是一个带有两个自定义参数的例子:
function CustomError(message, param1, param2) {
var err = new Error(message);
Object.setPrototypeOf(err, CustomError.prototype);
err.param1 = param1;
err.param2 = param2;
return err;
}
CustomError.prototype = Object.create(
Error.prototype,
{name: {value: 'CustomError', enumerable: false}}
);
使用示例:
try {
throw new CustomError('Something Unexpected Happened!', 1234, 'neat');
} catch (ex) {
console.log(ex.name); //CustomError
console.log(ex.message); //Something Unexpected Happened!
console.log(ex.param1); //1234
console.log(ex.param2); //neat
console.log(ex.stack); //stacktrace
console.log(ex instanceof Error); //true
console.log(ex instanceof CustomError); //true
}
对于需要setPrototypeOf的polyfil的环境:
Object.setPrototypeOf = Object.setPrototypeOf || function (obj, proto) {
obj.__proto__ = proto;
return obj;
};
Mohsen has a great answer above in ES6 that sets the name, but if you're using TypeScript or if you're living in the future where hopefully this proposal for public and private class fields has moved past stage 3 as a proposal and made it into stage 4 as part of ECMAScript/JavaScript then you might want to know this is then just a little bit shorter. Stage 3 is where browsers start implementing features, so if your browser supports it the code below just might work. (Tested in the new Edge browser v81 it seems to work fine). Be warned though this is an unstable feature at the moment and should be used cautiously and you should always check browser support on unstable features. This post is mainly for those future dwellers when browsers might support this. To check support check MDN and Can I use. It's currently got 66% support across the browser market which is getting there but not that great so if you really want to use it now and don't want to wait either use a transpiler like Babel or something like TypeScript.
类EOFError扩展错误{ name = " EOFError " } 抛出新的EOFError("Oops error ");
将此与一个无名错误进行比较,该错误在抛出时不会记录其名称。
类NamelessEOFError扩展错误{} 抛出新的NamelessEOFError("Oops error ");
如果你不关心错误的性能,这是你能做的最小的
Object.setPrototypeOf(MyError.prototype, Error.prototype)
function MyError(message) {
const error = new Error(message)
Object.setPrototypeOf(error, MyError.prototype);
return error
}
你可以不使用new只使用MyError(message)
通过在构造函数Error被调用后更改原型,我们不必设置调用堆栈和消息
在ES6:
class MyError extends Error {
constructor(message) {
super(message);
this.name = 'MyError';
}
}
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