Javascript define variable notation question -

saw js notation today i've never seen before, bear me if common knows.

var cookiepath = cookiepath || ''; 

now, saying, if variable named cookiepath exists, set cookiepath or if doesn't, set ''?

the cookiepath variable being declared, initialized.

the var statement doesn't make harm if identifier declared in current lexical scope.

if cookiepath wasn't declared yet, var statement, before run-time, initialize variable undefined.

after that, in run-time, assignment made, if it's value falsy (other null, undefined, empty string, 0, nan, or false) it's set empty string.

keep in mind have access cookiepath variable in local scope.

consider following example:

var cookiepath = 'outer'; (function () {     var cookiepath = cookiepath || "";     alert(cookiepath); // alerts empty string, not "outer" })(); 

in above example, have global cookiepath variable, on global scope, when function executed, local cookiepath variable declared on scope of function, , shadows value of outer scope, , behavior noticeable before var statement in function, e.g.:

var foo = 'foo'; (function () {     alert(foo); // undefined, not 'foo' outer scope     var foo; // undefined })();