Javascript console.log(object) vs. concatenating string

Question

I\'m running this in node.js:

> x = { \'foo\' : \'bar\' }
{ foo: \'bar\' }
> console.log(x)
{ foo: \'bar\' }
undefined
> console.log(\"hmm: \" + x)
         


        

Answer 1

The console.log function

'console.log' is an overloaded function that accepts a list of parameters that are either passed by copy (string|number|boolean) or by reference (everything else).

In the case of values passed by copy, the value is printed by casting it as a string.
In the case of values passed by reference, the value is pretty printed as the browser sees fit.

The + operator

The plus sign operator (+) is overloaded. When both sides of the operator are numbers, the sum of the two operators is returned.

If either side of the operator is a string, then both sides will be cast as string and the concatenation of those two strings will be returned.

console.log("hmm: " + x);

is the same as writing

console.log(String("hmm: ") + String(x));

Solution

Prevent the implicit string casting by swapping the plus sign (+) with a comma (,)

console.log("hmm: ", x);

More Info

For a more in depth description of the 'console.log' function, see:
https://developer.mozilla.org/en-US/docs/DOM/console.log

For a more in depth description on the plus sign operator (+), see:
http://www.w3schools.com/js/js_operators.asp