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
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
其他回答
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
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
}
function InvalidValueError(value, type) {
this.message = "Expected `" + type.name + "`: " + value;
var error = new Error(this.message);
this.stack = error.stack;
}
InvalidValueError.prototype = new Error();
InvalidValueError.prototype.name = InvalidValueError.name;
InvalidValueError.prototype.constructor = InvalidValueError;
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:
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());
}
});
