出于某种原因,在下面的代码段中,构造函数委托似乎不起作用:

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

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

运行该命令得到的消息是:"。有什么想法,为什么,或者是否有更好的方法来创建一个新的错误子类?是否有一个问题,应用到本机错误构造函数,我不知道?


当前回答

这是最快的方法:

    let thisVar = false

    if (thisVar === false) {
            throw new Error("thisVar is false. It should be true.")
    }

其他回答

另一种替代方法可能并不适用于所有环境。至少可以保证它在nodejs 0.8中工作 这种方法使用了一种非标准的方法来修改内部原型道具

function myError(msg){ 
      var e = new Error(msg); 
      _this = this; 
      _this.__proto__.__proto__ = e;
}

如果你使用Node/Chrome。下面的代码片段将为您提供满足以下要求的扩展。

err instanceof Error err instanceof CustomErrorType console.log() returns [CustomErrorType] when created with a message console.log() returns [CustomErrorType: message] when created without a message throw/stack provides the information at the point the error was created. Works optimally in Node.JS, and Chrome. Will pass instanceof checks in Chrome, Safari, Firefox and IE 8+, but will not have a valid stack outside of Chrome/Safari. I'm OK with that because I can debug in chrome, but code which requires specific error types will still function cross browser. If you need Node only you can easily remove the if statements and you're good to go.

片段

var CustomErrorType = function(message) {
    if (Object.defineProperty) {
        Object.defineProperty(this, "message", {
            value : message || "",
            enumerable : false
        });
    } else {
        this.message = message;
    }

    if (Error.captureStackTrace) {
        Error.captureStackTrace(this, CustomErrorType);
    }
}

CustomErrorType.prototype = new Error();
CustomErrorType.prototype.name = "CustomErrorType";

使用

var err = new CustomErrorType("foo");

输出

var err = new CustomErrorType("foo");
console.log(err);
console.log(err.stack);

[CustomErrorType: foo]
CustomErrorType: foo
    at Object.<anonymous> (/errorTest.js:27:12)
    at Module._compile (module.js:456:26)
    at Object.Module._extensions..js (module.js:474:10)
    at Module.load (module.js:356:32)
    at Function.Module._load (module.js:312:12)
    at Function.Module.runMain (module.js:497:10)
    at startup (node.js:119:16)
    at node.js:906:3

/errorTest.js:30
        throw err;
              ^
CustomErrorType: foo
    at Object.<anonymous> (/errorTest.js:27:12)
    at Module._compile (module.js:456:26)
    at Object.Module._extensions..js (module.js:474:10)
    at Module.load (module.js:356:32)
    at Function.Module._load (module.js:312:12)
    at Function.Module.runMain (module.js:497:10)
    at startup (node.js:119:16)
    at node.js:906:3

这部分的标准可以解释为什么错误。Apply调用不会初始化对象:

15.11.1错误构造函数作为函数调用 当Error作为函数而不是构造函数调用时,它会创建和 初始化一个新的Error对象。因此函数调用Error(…)是 等价于对象创建表达式new Error(… 相同的参数。

在这种情况下,Error函数可能确定它没有作为构造函数被调用,因此它返回一个新的Error实例,而不是初始化this对象。

用下面的代码进行测试似乎证明了这就是实际发生的情况:

function NotImplementedError() { 
   var returned = Error.apply(this, arguments);
   console.log("returned.message = '" + returned.message + "'");
   console.log("this.message = '" + this.message + "'");
}
NotImplementedError.prototype = new Error();

var nie = new NotImplementedError("some message");

运行此命令时输出如下:

returned.message = 'some message'
this.message = ''

我只需要实现这样的东西,发现堆栈在我自己的错误实现中丢失了。我要做的是创建一个虚拟错误,并从中检索堆栈:

My.Error = function (message, innerException) {
    var err = new Error();
    this.stack = err.stack; // IMPORTANT!
    this.name = "Error";
    this.message = message;
    this.innerException = innerException;
}
My.Error.prototype = new Error();
My.Error.prototype.constructor = My.Error;
My.Error.prototype.toString = function (includeStackTrace) {
    var msg = this.message;
    var e = this.innerException;
    while (e) {
        msg += " The details are:\n" + e.message;
        e = e.innerException;
    }
    if (includeStackTrace) {
        msg += "\n\nStack Trace:\n\n" + this.stack;
    }
    return msg;
}

我喜欢这样做:

利用name,使toString()抛出"{code}: {message}" 将相同的东西返回给super,这样在stacktrace中就会显示相同的内容 将代码附加到错误。在代码中检查/解析代码比检查消息(例如,您可能希望本地化消息)更好 将消息附加到错误。message作为error.toString()的替代

class AppException extends Error { constructor(code, message) { const fullMsg = message ? `${code}: ${message}` : code; super(fullMsg); this.name = code; this.code = code; this.message = fullMsg; } toString() { return this.message; } } // Just a code try { throw new AppException('FORBIDDEN'); } catch(e) { console.error(e); console.error(e.toString()); console.log(e.code === 'FORBIDDEN'); } // A code and a message try { throw new AppException('FORBIDDEN', 'You don\'t have access to this page'); } catch(e) { console.error(e); console.error(e.toString()); console.log(e.code === 'FORBIDDEN'); }