If you just make sure to always use === then this is exactly what happens. You can use tools like jslint to warn you if you accidentally use ==

Not quite though. I had a bug with Javascript where I was reading in a number and forgot to parse it to a float. I ended up doing an addition with that value, which later got used as a float again. So I had 1 + "10" turn to 110 when I tried to use it. No == or === anywhere.

I was only really referring to automatic type conversion for comparisons. That said, the example you gave sounds like the opposite, where you wanted it to do some auto-conversion and you're disappointed that it didn't? If I did 1 + "10" I don't think I'd want it to return 11!

I'd want it to throw some kind of cast exception, personally, not try and do what it thinks I want. (I'm not the GP)

It did convert the value. It converted the 1 to a string and added "10" to the end of it, resulting in "110" which then was converted to a float and used.

The error in this case would be forgetting Javascript's rules of implicit conversion.

Adding a float to a string results in a string.

That just fixes one of javascript's weirdnesses. There are many many others.