Question

I’m investigating Three.js at the moment and have come across this variable declaration at the top of the main source file:

var THREE = THREE || { REVISION: '52' };

I’m just wondering what the OR (||) is doing in there – what is the function of it?

Answer 1

The above means:

If the value of THREE evaluates to true, assign the value of THREE to the THREE variable, otherwise initialize it to the object { REVISION: '52' }.