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
这并不复杂,但我个人认为这是扩展错误的最简单方法。
export default class ExtendableError extends Error {
constructor(message) {
super(message);
this.name = this.constructor.name;
}
}
创建一个名为ExtendableError的实用程序类。这个实用程序类的目的是与普通的Error类类似,但在默认情况下将name属性更改为类的名称,因此很容易扩展错误。
现在,如果您想扩展一个错误,它只需要一行。
class MyError extends ExtendableError {}
其他回答
我想再补充一下大家已经说过的话:
为了确保自定义错误类在堆栈跟踪中正确显示,您需要将自定义错误类的原型的name属性设置为自定义错误类的name属性。 我的意思是:
CustomError.prototype = Error.prototype;
CustomError.prototype.name = 'CustomError';
完整的例子是:
var CustomError = function(message) {
var err = new Error(message);
err.name = 'CustomError';
this.name = err.name;
this.message = err.message;
//check if there is a stack property supported in browser
if (err.stack) {
this.stack = err.stack;
}
//we should define how our toString function works as this will be used internally
//by the browser's stack trace generation function
this.toString = function() {
return this.name + ': ' + this.message;
};
};
CustomError.prototype = new Error();
CustomError.prototype.name = 'CustomError';
当所有的都说了,做了,你抛出你的新异常,它看起来像这样(我懒惰地尝试在chrome开发工具):
CustomError: Stuff Happened. GASP!
at Error.CustomError (<anonymous>:3:19)
at <anonymous>:2:7
at Object.InjectedScript._evaluateOn (<anonymous>:603:39)
at Object.InjectedScript._evaluateAndWrap (<anonymous>:562:52)
at Object.InjectedScript.evaluate (<anonymous>:481:21)
我会退一步考虑你为什么要这么做?我认为关键是要以不同的方式处理不同的错误。
例如,在Python中,您可以限制catch语句仅捕获MyValidationError,也许您希望能够在javascript中执行类似的操作。
catch (MyValidationError e) {
....
}
你不能在javascript中这样做。只有一个捕捉块。你应该对错误使用if语句来确定它的类型。
抓住(e) { 如果(isMyValidationError (e)) { ... }其他{ //可能重新抛出? 把e; } }
我想我会抛出一个原始对象,其中包含类型、消息和您认为合适的任何其他属性。
throw { type: "validation", message: "Invalid timestamp" }
当你捕捉到错误时:
catch(e) {
if(e.type === "validation") {
// handle error
}
// re-throw, or whatever else
}
为了避免针对每种不同类型的错误的样板文件,我将一些解决方案的智慧结合到createErrorType函数中:
function createErrorType(name, init) {
function E(message) {
if (!Error.captureStackTrace)
this.stack = (new Error()).stack;
else
Error.captureStackTrace(this, this.constructor);
this.message = message;
init && init.apply(this, arguments);
}
E.prototype = new Error();
E.prototype.name = name;
E.prototype.constructor = E;
return E;
}
然后,您可以轻松地定义新的错误类型,如下所示:
var NameError = createErrorType('NameError', function (name, invalidChar) {
this.message = 'The name ' + name + ' may not contain ' + invalidChar;
});
var UnboundError = createErrorType('UnboundError', function (variableName) {
this.message = 'Variable ' + variableName + ' is not bound';
});
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 ");
我建议的解决方案是使用error的.name属性来区分错误类型,而不是instancof
这并没有完全回答问题,但我认为这是一个合理的解决方案,至少在某些情况下。
我所看到的能够拥有一个instanceof CustomError的好处是,您可以在promise catch处理程序中进行自定义处理。
例如:
class CustomError extends Error {/** ... **/}
axios
.post(url, payload)
.then(data => {
if (!data.loggedIn) throw CustomError("not logged in");
return data;
})
.catch(error => {
if (error instanceof CustomError) {/** custom handling of error*//}
throw error
})
如果这是你想要达到的目的,.name参数也很适合你:
export const ERROR_NOT_LOGGED_IN = "ERROR_NOT_LOGGED_IN";
axios
.post(url, payload)
.then(data => {
if (!data.loggedIn) throw Error("not logged in").name=ERROR_NOT_LOGGED_IN ;
return data;
})
.catch(error => {
if (error.name === ERROR_NOT_LOGGED_IN) {/** custom handling of error*//}
throw error
})