Use coffeescript/javascript 'throw error' or 'throw new Error(error)'?
Same as in other languages like C# or Java:
-
throw error
throws the same Error object -
throw new Error(error)
wraps it into a new Error object. The later is used, for example, in Java when you need to convert checked Exception into unchecked one. In JavaScript you don't need to wrap exceptions as this would make stacktrace a bit longer and less pretty.
Edit: There're some security implications as well. Here's an example:
function noWrap() {
try {
var o = {}; o.nonexistingMethod();
} catch (error) {
throw error;
}
}
function wrap() {
try {
var o = {}; o.nonexistingMethod();
} catch (error) {
throw new Error(error);
}
}
Calling noWrap()
produces the following error message:
"TypeError: Object #<Object> has no method 'nonexistingMethod'"
// with error.arguments === ['nonexistingMethod', o]
Calling wrap()
produces the following error message:
"Error: TypeError: Object #<Object> has no method 'nonexistingMethod'"
// with error.arguments === undefined
So, as you can see by using a wrapping Error object we can hide the arguments
of original error. Suppose you're writing one of the following:
- some kind of a library
- a script which will be loaded on a page that you don't own (for example, some kind of like or tweet button)
- a script on a page that has some third-party scripts loaded (social buttons, ads, tracking code, etc.)
In all those cases listed above in order to stay secure you should wrap your Error
objects. Otherwise you may accidentally leak references to your internal objects, functions and variables.
Edit 2: Regarding stacktraces. Both variants preserve them. Here's a working example and I get the following stacktraces in Chrome:
// No wrapping:
TypeError: Object #<Object> has no method 'nonexistingMethod'
at noWrap (http://fiddle.jshell.net/listochkin/tJzCF/show/:22:23)
at http://fiddle.jshell.net/listochkin/tJzCF/show/:37:5
at http://fiddle.jshell.net/js/lib/mootools-core-1.4.5-nocompat.js:3901:62
at http://fiddle.jshell.net/js/lib/mootools-core-1.4.5-nocompat.js:3915:20
// Wrapping:
Error: TypeError: Object #<Object> has no method 'nonexistingMethod'
at wrap (http://fiddle.jshell.net/listochkin/tJzCF/show/:32:15)
at http://fiddle.jshell.net/listochkin/tJzCF/show/:44:5
at http://fiddle.jshell.net/js/lib/mootools-core-1.4.5-nocompat.js:3901:62
at http://fiddle.jshell.net/js/lib/mootools-core-1.4.5-nocompat.js:3915:20
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Mihai Oprea
I solve problems. http://blog.mihaioprea.com LinkedIn: http://ro.linkedin.com/pub/mihai-oprea/8/44a/82 Twitter: http://twitter.com/#!/mishu21
Updated on September 16, 2022Comments
-
Mihai Oprea over 1 year
I have the following coffeescript code:
try do something catch error log something throw error
Should I use
throw new Error(error)
instead ofthrow error
?What is the difference?
-
Mihai Oprea almost 12 yearsSomeone advised me that the wrapped version gives you an error object with a full stacktrace, otherwise you only get the error message.
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Andrei Андрей Листочкин almost 12 yearsIt's browser-dependent. For example, In IE9 there's no
stack
property on Error objects. I don't know about other browsers.