How to handle an Error correctly using Javascript?

when i want to send and Error using Javascript i do:

throw new Error()

it works, but if i pass a number, example:

throw new Error(500)

Th开发者_如何学Goe result is:

Error: 500

Where 'Error: ' is a string.

I have a function that handle this errors, this function must to know the code of the error, how to retrieve it? Do i have to parse the string? :-(

Thank you.

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If you throw an error that way, the text between parenthesis becomes the error message. You can also throw using a custom Error Object.

A very useful link: The art of throwing JavaScript errors

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Error instances have a message property, and that's what you should analyze, not what it prints into console (which is Error.prototype.toString).

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See https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Error - the error message is always a string. Even if you pass a number to it, it will be implicitly converted to a string.

Error: 500 is the default string representation of an Error object - that's what you get if you convert this object to a string or call error.toString() directly. If you are interested in the error message you should access the message directly - parseInt(error.message, 10) should do.

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I highly recommend against throwing errors. Try catch is expensive and one slip up will mean your server shuts down.

I recommend you use the event approach, include eventemitters is most of your code.

That way you can just do this.emit("error", new Error(500))

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If I get what you're saying, extract the number using some RegExp?

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You don't actually need to use the Error object. You can just write throw followed by whatever you want to be caught by a catch block. This little code snippet displays 500 in the alert box.

function throwError(msg){
    throw msg;
}
try{
    throwError(500);
}catch(e){
    alert(e);
}

If you test e with typeof it returns number.