Question

I’m testin some JavaScript concepts and I’m trying to understand why:

typeof({} + {})
typeof([] + [])

return a ‘string’ yet:

typeof {}
typeof []

return an ‘object’

I’ve tried this in NodeJS, FireFox, Chrome and IE9 all with the same results.

Answer 1

The + operator is defined to either concatenate strings or add numbers. If you try something else, the operands have to be converted to strings or numbers first. It looks like string is preferred here.

You can control what string or number is returned by defining functions .toString and .valueOf on the objects respectively