Question

I just started to read some JavaScript project. Most of the .js file to start with have an object declared as the following:

window.Example || {
bleh: "123";
blah: "ref"
}

What does the || symbol do here?

Answer 1

Objects in Javascript are truthy, so that expression evaluates to either window.Example or the default object if window.Example is falsy (or undefined). Example:

var x = window.Example || {foo: 'bar'};
// x = {foo: 'bar'}, since window.Example is undefined

window.Example = {test: 1};

var y = window.Example || {foo: 'bar'};
// y = {test: 1}, since window.Example is truthy (all objects are truthy)

Read this article for a good explanation on truthy/falsy and short-circuit evaluation.