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
class NotImplementedError extends Error {
constructor(message) {
super(message);
this.message = message;
}
}
NotImplementedError.prototype.name = 'NotImplementedError';
module.exports = NotImplementedError;
and
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);
}
它只是这个答案的一个类表示。
输出
NotImplementedError: NotImplementedError message
...stacktrace
ex1 instanceof NotImplementedError = true
ex1 instanceof Error = true
ex1.name = NotImplementedError
ex1.message = NotImplementedError message
其他回答
我使用构造函数模式来创建新的错误对象。我定义了原型链，比如Error实例。请参阅MDN错误构造函数参考。
你可以查看这段关于要点的片段。
实现
// Creates user-defined exceptions
var CustomError = (function() {
'use strict';
//constructor
function CustomError() {
//enforces 'new' instance
if (!(this instanceof CustomError)) {
return new CustomError(arguments);
}
var error,
//handles the arguments object when is passed by enforcing a 'new' instance
args = Array.apply(null, typeof arguments[0] === 'object' ? arguments[0] : arguments),
message = args.shift() || 'An exception has occurred';
//builds the message with multiple arguments
if (~message.indexOf('}')) {
args.forEach(function(arg, i) {
message = message.replace(RegExp('\\{' + i + '}', 'g'), arg);
});
}
//gets the exception stack
error = new Error(message);
//access to CustomError.prototype.name
error.name = this.name;
//set the properties of the instance
//in order to resemble an Error instance
Object.defineProperties(this, {
stack: {
enumerable: false,
get: function() { return error.stack; }
},
message: {
enumerable: false,
value: message
}
});
}
// Creates the prototype and prevents the direct reference to Error.prototype;
// Not used new Error() here because an exception would be raised here,
// but we need to raise the exception when CustomError instance is created.
CustomError.prototype = Object.create(Error.prototype, {
//fixes the link to the constructor (ES5)
constructor: setDescriptor(CustomError),
name: setDescriptor('JSU Error')
});
function setDescriptor(value) {
return {
configurable: false,
enumerable: false,
writable: false,
value: value
};
}
//returns the constructor
return CustomError;
}());
使用
CustomError构造函数可以接收许多参数来构建消息，例如:
var err1 = new CustomError("The url of file is required"),
err2 = new CustomError("Invalid Date: {0}", +"date"),
err3 = new CustomError("The length must be greater than {0}", 4),
err4 = new CustomError("Properties .{0} and .{1} don't exist", "p1", "p2");
throw err4;
这是自定义错误的样子:
我也遇到过类似的问题。我的错误需要是error和NotImplemented的实例，它还需要在控制台中产生一致的回溯。
我的解决方案:
var NotImplemented = (function() {
var NotImplemented, err;
NotImplemented = (function() {
function NotImplemented(message) {
var err;
err = new Error(message);
err.name = "NotImplemented";
this.message = err.message;
if (err.stack) this.stack = err.stack;
}
return NotImplemented;
})();
err = new Error();
err.name = "NotImplemented";
NotImplemented.prototype = err;
return NotImplemented;
}).call(this);
// TEST:
console.log("instanceof Error: " + (new NotImplemented() instanceof Error));
console.log("instanceof NotImplemented: " + (new NotImplemented() instanceofNotImplemented));
console.log("message: "+(new NotImplemented('I was too busy').message));
throw new NotImplemented("just didn't feel like it");
使用node.js运行的结果:
instanceof Error: true
instanceof NotImplemented: true
message: I was too busy
/private/tmp/t.js:24
throw new NotImplemented("just didn't feel like it");
^
NotImplemented: just didn't feel like it
at Error.NotImplemented (/Users/colin/projects/gems/jax/t.js:6:13)
at Object.<anonymous> (/Users/colin/projects/gems/jax/t.js:24:7)
at Module._compile (module.js:449:26)
at Object.Module._extensions..js (module.js:467:10)
at Module.load (module.js:356:32)
at Function.Module._load (module.js:312:12)
at Module.runMain (module.js:487:10)
at process.startup.processNextTick.process._tickCallback (node.js:244:9)
该错误通过了我的所有3个标准，尽管stack属性是非标准的，但在大多数较新的浏览器中都支持它，这在我的情况下是可以接受的。
MDN有一个很好的例子:
try {
throw new Error('Whoops!');
} catch (e) {
console.log(e.name + ': ' + e.message);
}
更简单的方法。你可以让你的对象从Error对象继承。 例子:
function NotImplementError(message)
{
this.message = message;
Error.call();
Error.call(message);
}
我们所做的是使用函数call()调用Error类的构造函数，因此基本上与在其他面向对象语言中实现类继承是一样的。
class NotImplementedError extends Error {
constructor(message) {
super(message);
this.message = message;
}
}
NotImplementedError.prototype.name = 'NotImplementedError';
module.exports = NotImplementedError;
and
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);
}
它只是这个答案的一个类表示。
输出
NotImplementedError: NotImplementedError message
...stacktrace
ex1 instanceof NotImplementedError = true
ex1 instanceof Error = true
ex1.name = NotImplementedError
ex1.message = NotImplementedError message
