CODEWITHSUNDEEP
javascripterror-handling
cc young
cc young

Reputation: 20213

in javascript, are there built-in error codes? is it possible to trap an internal error? possible to continue?

ok, I feel stupid asking this question, and forgive my poor research techniques, but...

using the example

  if( obj.attr1.attr2.attr3 == 'constant' ) return;
  else if( condition2 ) ...

if obj.attr1 is undefined, the javascript engine throws an error.

  1. what is the error that is thrown? is it universally defined?

  2. is is possible to globally trap this error?

  3. if trapped, is it possible for the next line condition2 to be executed?

to clarify: the error is raised because trying to get attribute of undefined. is there any way to know that this is the error being raised? is it in some table of standard javascript error messages?

and second, having trapped the error upstream, is it possible for program to flow uninterruptedly?

Upvotes: 4

Views: 975

Answers (2)

Mutation Person
Mutation Person

Reputation: 30500

It's possible to trap this error with a try/catch block:

try{
    if( obj.attr1.attr2.attr3 == 'constant' ) {
        alert("test");
    }
}
catch(e)
{
    alert(e.Message);
}

The exception gives you the following:

description "'obj' is undefined"    String
message    "'obj' is undefined" String
name    "TypeError" String
number  -2146823279 Number

Upvotes: 2

Tomalak
Tomalak

Reputation: 338228

Usually this is solved gracefully by not blindly assuming that something is there.

if( obj.attr1 && obj.attr1.attr2 && obj.attr1.attr2.attr3 == 'constant' )

Other than that, you can write a try/catch statement that catches the exception here, but using structured exception handling to direct the normal program flow is frowned upon and should be avoided.

Upvotes: 0

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