Question

x = ( typeof x != 'undefined' && x instanceof Array ) ? x : [];

I understand that if x is defined and it is an array it will do everything between ? and : then if undefined or it is not an array it will do []. what is []?

Does anyone know where i can get examples of how this works and other shorthand techniques or can you explain what is happening here?

I just really dont understand how it is creating an array

Answer 1

[] is an empty array.

So if x is undefined or not an array, then it is set to an empty array.

This is the same as:

if (!( typeof x != 'undefined' && x instanceof Array )) {
    x = [];
}

There is more information on the Conditional (Ternary) Operator here:

http://msdn.microsoft.com/en-us/library/windows/apps/be21c7hw%28v=vs.94%29.aspx

Another useful shorthand for default arguments is:

function (x) {
    x = x || 7;
}

This is set x to 7 as long as x == false (i.e. x is not null, undefined, false, '' (empty string), or 0)