未在javascript中调用函数

Question

I have the following code:

function isVisible(selector) {
    $(selector).is(':visible');
}

var isMapVisible;
var initialWindowWidth = window.innerWidth;
/* Window Resize Helper */
function handleWindowResize() {
    isMapVisible = isVisible('.search__map');
    if (window.innerWidth > 768) {
        var windowHeight = window.innerHeight,
        searchResultsHeight = windowHeight - $('.search__results').position().top,
        searchMapHeight = windowHeight - $('.search__map').position().top;
        $('.search__results').height(searchResultsHeight);
        $('.search__map').height(searchMapHeight);
        if (initialWindowWidth < 769) {
            /* 
                This is a hack to trigger the map to show up if initial windowWidth causes the map to hide. 
                it only triggers once.
            */
            resizeMap();
            map.setZoom(map.getZoom() - 1);
            initialWindowWidth = 1000;
        }
    } else {
        $('.search__results').height('auto');
    }
}

And in the function handleWindowResize() , I had a variable that I set globally as isMapVisible . and is calling another function isVisible() . I found out that when I replace that line of code with isMapVisible = $('.search__map').is(':visible') , I am able to get the correct result, but if my code is as copied above, I would get undefined. Any idea why?

Answer 1

That is because you are not returning anything in your function:

function isVisible(selector) {
    return $(selector).is(':visible');
}