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
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。
其他回答
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。
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
以下是我支持es2015之前版本浏览器的解决方案。它不做任何花哨的原型调整，也不会破坏调试器。
/** Custom Errors
// Depends on underscore js
// This will declare an CustError() class in both 'this' and '_exports' namespaces
// ctor is optional
declare_cust_error(function CustError(){}, {ns: [this, _exports], ctor:
function cust_err_ctor(instance, clazz, name, msg, info){
q$.called(arguments)
}
})
// Usage:
// Second param (pojso) is optional
try {
throw CustError.create("foo", {k1: 'v1', k2: 'v2'})
}catch(ex){
if(CustError.is_inst(ex)){
console.error("its a CustError", ex)
} else {
throw ex
}
}
**/
function declare_cust_error(error_class, opts){
var p, c, cp
if(!error_class||!(p=error_class.prototype))throw new Error("error_class must be a Class")
try{
c = p.constructor; cp = c.toString()
}catch(ex){}
if(!cp || cp.indexOf('function ') != 0 || cp.indexOf('[native code]') > 0)
throw new Error("error_class must be a classic proto class (pre-es6) but got: " + error_class.toString())
opts=opts||{}
error_class.__is_cust_error__ = true
error_class.__cust_error_name__ = c.name
error_class.create = function cust_error_create(msg, info){
var instance = new Error(msg)
instance.info = info
instance.__is_cust_error__ = true
instance.__cust_error_name__ = c.name
if(_.isFunction(opts.ctor)){
opts.ctor(instance, error_class, c.name, msg, info)
}
return instance
}
error_class.is_inst = function cust_error_is_inst(instanace){
return ( (instanace instanceof Error) && instanace.__cust_error_name__ === error_class.__cust_error_name__ )
}
// Declare error in namespace(s)
_.each(_.isArray(opts.ns)?opts.ns:[opts.ns], function(ns){ ns[c.name] = error_class })
return error_class
}
这是我的实现:
class HttpError extends Error {
constructor(message, code = null, status = null, stack = null, name = null) {
super();
this.message = message;
this.status = 500;
this.name = name || this.constructor.name;
this.code = code || `E_${this.name.toUpperCase()}`;
this.stack = stack || null;
}
static fromObject(error) {
if (error instanceof HttpError) {
return error;
}
else {
const { message, code, status, stack } = error;
return new ServerError(message, code, status, stack, error.constructor.name);
}
}
expose() {
if (this instanceof ClientError) {
return { ...this };
}
else {
return {
name: this.name,
code: this.code,
status: this.status,
}
}
}
}
class ServerError extends HttpError {}
class ClientError extends HttpError { }
class IncorrectCredentials extends ClientError {
constructor(...args) {
super(...args);
this.status = 400;
}
}
class ResourceNotFound extends ClientError {
constructor(...args) {
super(...args);
this.status = 404;
}
}
示例用法#1:
app.use((req, res, next) => {
try {
invalidFunction();
}
catch (err) {
const error = HttpError.fromObject(err);
return res.status(error.status).send(error.expose());
}
});
示例用法#2:
router.post('/api/auth', async (req, res) => {
try {
const isLogged = await User.logIn(req.body.username, req.body.password);
if (!isLogged) {
throw new IncorrectCredentials('Incorrect username or password');
}
else {
return res.status(200).send({
token,
});
}
}
catch (err) {
const error = HttpError.fromObject(err);
return res.status(error.status).send(error.expose());
}
});
根据Joyent的说法，你不应该乱搞堆栈属性(我在这里给出的很多答案中看到了)，因为它会对性能产生负面影响。他们是这么说的:
Stack:一般来说，不要搞砸这个。甚至不要扩大它。V8只在有人实际读取属性时才计算它，这极大地提高了可处理错误的性能。如果读取属性只是为了扩充它，即使调用者不需要堆栈，最终也会付出代价。
我喜欢并想要提到他们的想法，包装原始错误，这是一个很好的替代传递堆栈。
下面是我如何创建一个自定义错误，考虑到上面提到的:
es5版本:
function RError(options) { options = options || {}; // eslint-disable-line no-param-reassign this.name = options.name; this.message = options.message; this.cause = options.cause; // capture stack (this property is supposed to be treated as private) this._err = new Error(); // create an iterable chain this.chain = this.cause ? [this].concat(this.cause.chain) : [this]; } RError.prototype = Object.create(Error.prototype, { constructor: { value: RError, writable: true, configurable: true } }); Object.defineProperty(RError.prototype, 'stack', { get: function stack() { return this.name + ': ' + this.message + '\n' + this._err.stack.split('\n').slice(2).join('\n'); } }); Object.defineProperty(RError.prototype, 'why', { get: function why() { var _why = this.name + ': ' + this.message; for (var i = 1; i < this.chain.length; i++) { var e = this.chain[i]; _why += ' <- ' + e.name + ': ' + e.message; } return _why; } }); // usage function fail() { throw new RError({ name: 'BAR', message: 'I messed up.' }); } function failFurther() { try { fail(); } catch (err) { throw new RError({ name: 'FOO', message: 'Something went wrong.', cause: err }); } } try { failFurther(); } catch (err) { console.error(err.why); console.error(err.stack); console.error(err.cause.stack); }
es6版本:
class RError extends Error { constructor({name, message, cause}) { super(); this.name = name; this.message = message; this.cause = cause; } [Symbol.iterator]() { let current = this; let done = false; const iterator = { next() { const val = current; if (done) { return { value: val, done: true }; } current = current.cause; if (!val.cause) { done = true; } return { value: val, done: false }; } }; return iterator; } get why() { let _why = ''; for (const e of this) { _why += `${_why.length ? ' <- ' : ''}${e.name}: ${e.message}`; } return _why; } } // usage function fail() { throw new RError({ name: 'BAR', message: 'I messed up.' }); } function failFurther() { try { fail(); } catch (err) { throw new RError({ name: 'FOO', message: 'Something went wrong.', cause: err }); } } try { failFurther(); } catch (err) { console.error(err.why); console.error(err.stack); console.error(err.cause.stack); }
我已经把我的解决方案放到了一个模块中，这里是:https://www.npmjs.com/package/rerror
