如何在 JavaScript 中创建自定义错误? [英] How do I create a custom Error in JavaScript?

问题描述

出于某种原因，构造函数委托在以下代码段中似​​乎不起作用:

For some reason it looks like constructor delegation doesn't work in the following snippet:

function NotImplementedError() { 
  Error.apply(this, arguments); 
}
NotImplementedError.prototype = new Error();

var nie = new NotImplementedError("some message");
console.log("The message is: '"+nie.message+"'")

运行这个给出消息是:''.关于原因的任何想法，或者是否有更好的方法来创建新的 Error 子类?apply 用于我不知道的本机 Error 构造函数是否有问题?

Running this gives The message is: ''. Any ideas as to why, or if there is a better way to create a new Error subclass? Is there a problem with applying to the native Error constructor that I don't know about?

推荐答案

更新你的代码，将你的原型分配给 Error.prototype，instanceof 和你的断言工作.

Update your code to assign your prototype to the Error.prototype and the instanceof and your asserts work.

function NotImplementedError(message = "") {
    this.name = "NotImplementedError";
    this.message = message;
}
NotImplementedError.prototype = Error.prototype;

但是，我只会抛出您自己的对象并检查 name 属性.

However, I would just throw your own object and just check the name property.

throw {name : "NotImplementedError", message : "too lazy to implement"}; 

根据评论进行编辑

在查看评论并试图记住为什么我会将原型分配给 Error.prototype 而不是 new Error() 就像 Nicholas Zakas 在他的 文章，我使用以下代码创建了一个 jsFiddle:

After looking at the comments and trying to remember why I would assign prototype to Error.prototype instead of new Error() like Nicholas Zakas did in his article, I created a jsFiddle with the code below:

function NotImplementedError(message = "") {
  this.name = "NotImplementedError";
  this.message = message;
}
NotImplementedError.prototype = Error.prototype;

function NotImplementedError2(message = "") {
  this.message = message;
}
NotImplementedError2.prototype = new Error();

try {
  var e = new NotImplementedError("NotImplementedError message");
  throw e;
} catch (ex1) {
  console.log(ex1.stack);
  console.log("ex1 instanceof NotImplementedError = " + (ex1 instanceof NotImplementedError));
  console.log("ex1 instanceof Error = " + (ex1 instanceof Error));
  console.log("ex1.name = " + ex1.name);
  console.log("ex1.message = " + ex1.message);
}

try {
  var e = new NotImplementedError2("NotImplementedError2 message");
  throw e;
} catch (ex1) {
  console.log(ex1.stack);
  console.log("ex1 instanceof NotImplementedError2 = " + (ex1 instanceof NotImplementedError2));
  console.log("ex1 instanceof Error = " + (ex1 instanceof Error));
  console.log("ex1.name = " + ex1.name);
  console.log("ex1.message = " + ex1.message);
}

控制台输出是这样的.

undefined
ex1 instanceof NotImplementedError = true
ex1 instanceof Error = true
ex1.name = NotImplementedError
ex1.message = NotImplementedError message
Error
    at window.onload (http://fiddle.jshell.net/MwMEJ/show/:29:34)
ex1 instanceof NotImplementedError2 = true
ex1 instanceof Error = true
ex1.name = Error
ex1.message = NotImplementedError2 message

这证实了问题"我遇到的是错误的堆栈属性是创建 new Error() 的行号，而不是 throw e 发生的地方.但是，这可能比具有影响 Error 对象的 NotImplementedError.prototype.name = "NotImplementedError" 行的副作用更好.

This confirmes the "problem" I ran into was the stack property of the error was the line number where new Error() was created, and not where the throw e occurred. However, that may be better that having the side effect of a NotImplementedError.prototype.name = "NotImplementedError" line affecting the Error object.

另外，注意NotImplementedError2，当我没有明确设置.name 时，它等于Error".但是，正如评论中提到的，因为该版本将原型设置为 new Error()，所以我可以设置 NotImplementedError2.prototype.name = "NotImplementedError2" 并且没问题.

Also, notice with NotImplementedError2, when I don't set the .name explicitly, it is equal to "Error". However, as mentioned in the comments, because that version sets prototype to new Error(), I could set NotImplementedError2.prototype.name = "NotImplementedError2" and be OK.

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