Javascript object changing automatically?

Question

I have the following code:

var doneFile=convertToMOSTEM(curFile.file,curFile.color,curFile.importance);
console.log('doneFile:');
console.log(doneFile);
debugger;
filesOS.add(doneFile);
debugger;

convertToMOSTEM returns a custom object. The console.log logs the custom object created by convertToMOSTEM to the console, but at the debugger statement directly after the console.log logs it as a different object. I do not wish to elaborate more about the contents of convertToMOSTEM, and am instead asking for situations where this can happen. I can say, however, that convertToMOSTEM creates a custom object with a custom constructor, and then it modifies some of the properties of that custom object, then returns the modified object. The console.log logs the correct version of the object, but the object that I get in the debugger statement is like a clean version of the custom object without the extra modifications applied by the convertToMOSTEM function. I am not sure if that is very clear, if you have any questions please ask me questions in the comments.

I don't see how that could happen. Can you set up a minimal working example that reproduces the problem? — bfavaretto, Jun 15 '13 at 02:42
this is weird. The isolated code works fine, but with other code in this file it messes up... — markasoftware, Jun 15 '13 at 03:13

score 1 · Answer 1 · answered Jun 15 '13 at 04:29

One possibility is that you're being misled by one bit of behavior that console.log() has that isn't obvious.

When you log an object, the console doesn't save all of the properties of that object for display later. The only real-time display is whatever the single-line printout from console.log() shows. If you click the triangle to expand an object that was displayed with console.log(), the expanded display shows the properties of that object at the time you click the triangle, not at the time of the original console.log() call.

To avoid this, log the individual properties you are interested in at the time of making the call. For example, if you have a person object with id, name, and email properties, don't do this:

console.log( person );

Do this instead:

console.log( person.id, person.name, person.email );

That way, if those three properties are string values, you will log their actual values at the time you make the console.log() call.

interesting, but even if this is true the object must be changing over time, even if it is the other way around, as it shows differently when I open the console.log arrow and when I see the variable in the debugger statement. +1 because this is good to know, but it doesn't solve the problem. — markasoftware, Jun 15 '13 at 04:34

Javascript object changing automatically?

1 Answers1