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?
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
}
上面的很多方法都不起作用。
最后一个是一个实际的错误。如果您使用字符串,它看起来很好,但它不会提供堆栈跟踪。如果你抛出错误,你不能有“Uncaught BadError: bad”,所以你必须删除自定义错误(遗憾的是)。如果你抛出一个对象,它看起来有点偏离,最后一个只是一个平均错误。
此方法创建一个具有自定义名称的错误,同时保留堆栈跟踪:
var errProto = Object.create(Error.prototype, {
constructor: {
value: Error,
enumerable: false,
writable: true,
configurable: true
}
})
var isFirefox = !!window.InstallTrigger
// Hide stack for Firefox only, as stacks can cause problems with high "frame" counts.
function createError(name, message, hideStack) {
if (message == null) {
message = ""
}
var customError = Error(message)
customError.name = name
Object.setPrototypeOf(customError, errProto)
if (isFirefox && hideStack) {
customError.stack = ""
} else if (isFirefox) {
var stack = customError.stack
var newline = stack.indexOf("\n") + 1
stack = stack.slice(newline)
customError.stack = stack
var split = stack.split(":")
if (split.length > 4) {
var a = split[3]
var b = split[4]
var t = b.slice(0, b.indexOf("\n"))
customError.lineNumber = Number(a)
customError.columnNumber = Number(t)
}
} else {
var stack = customError.stack
var split = stack.split("\n")
var secondPart = split.slice(2).join("\n")
stack = split[0] + "\n" + secondPart
customError.stack = stack
var split = secondPart.split(":")
var a = split[2]
var b = split[3]
}
throw customError
}
var frame = 0
function aFunction() {
if (++frame === 100) {
createError("LazyError", "function getting lazy", false, true)
} else {
requestAnimationFrame(aFunction)
}
}
setTimeout(aFunction, Math.random() * 500)
* {
font-family: Verdana;
}
Check your inspector!
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');
}