Question

Possible Duplicate:
Javascript Shorthand – What Does the '||' Operator Mean When Used in an Assignment?

var variable = obj1 || obj2;

Does it mean this?

var variable;

if (obj1)
{
    variable = obj1;
}
else if (obj2)
{
    variable = obj2:
}

Is it considered bad practise?

Answer 1

The || operator returns its left hand side if resolves to be a true value, otherwise it returns its right hand side.

So it means the same as:

var variable;
if (obj1){
    variable = obj1;
} else {
    variable = obj2:
}

Note else, not, else if.

It is a common pattern and not usually considered bad practise.

The gotcha is that you need to be sure you want if (obj) and not if (typeof obj !== "undefined").