How to return variable from jquery function

You don't need to return. Try this:

var height = $(window).height(); // define "height" here

$(window).resize(function(){
    height = $(window).height(); // update "height" variable, 
                                 // don't user "var" here.
                                 // because using "var" will redefine
                                 // "height" again and no longer contain the
                                 // updated value on window resize 
                                 // out of this resize function scope
});

setInterval(function() {
    $('div').append( 'Index: ' +  height );
}, 500);

When you use var you're creating a new variable, not overwriting the original. You'll want this instead:

var height = $(window).height();

$(window).resize(function() {
    height = $(window).height();
});

// ...

I suppose the answer to your question depends on how you want to return it. Console? Alert? A div or other element? See below for a list.

• console.log(height)
• alert(height)
• $("#elementID").html(height); // or whatever selector and method work for your case

I suppose you could also convert that $(window).resize block into a function, then call that function. That should work, too.