jQuery窗口调整大小无法正常工作

Question

Pseudocode:

1. If the window size equal to / or greater than 768 take content from the #sidebar and enter it in the place-holder div
2. If the window size is less than 768, do not run the above.

My jQuery code is as following:

$(document).ready(function () {

    var $window = $(window);

    function checkWidth() {
        //set main vars
        var windowsize = $window.width();
        var $sideBarContent = $('#sidebar .dummy-content');
        var $placeHolder = $('#place-holder');

        //perform the main check
        if (windowsize >= 768 && $('#place-holder').length) {
            $($sideBarContent).clone(true)
                .appendTo($($placeHolder));
        }
        else {
            $($placeHolder).hide();
        }
    }

    // Execute on load
    checkWidth();
    // Bind event listener
    $(window).resize(checkWidth);

});

But the problem is that at the first page load everything is performed well, but at resize and back again, the script is not doing his job. Also on each resize all the content from the sidebar, is entered several times into the placeholder (instead of once).

And my working jsfiddle.

I just do not know what I'm doing wrong.

Answer 1

A few problems:

• Your logic to add the new items is always true (as you only check whether the element exists - it always does).
• Your child check needs to be inside the width check (separate check).
• You need to show the placeHolder div again!
• You have some redundant $() around jQuery variables
• You have jQuery variables, for all the required elements, but sometimes you do not use them.

eg

$(document).ready(function () {

    var $window = $(window);

    function checkWidth() {
        //set main vars
        var windowsize = $window.width();
        var $sideBarContent = $('#sidebar .dummy-content');
        var $placeHolder = $('#place-holder');

        //perform the main check
        if (windowsize >= 768) {
            if (!$placeHolder.children().length) {
                $sideBarContent.clone(true)
                    .appendTo($placeHolder);
            }
            $placeHolder.show();
        } else {
            $placeHolder.hide();
        }
    }

    // Bind event listener and do initial execute
    $window.resize(checkWidth).trigger("resize");
});

JSFiddle: http://jsfiddle.net/TrueBlueAussie/jtfv4jjt/8/

Note: Your code can be simplified further as you only need to clone once at start and then just toggle visibility of that panel.

eg

$(document).ready(function () {

    var $window = $(window);
    var $sideBarContent = $('#sidebar .dummy-content');
    var $placeHolder = $('#place-holder');

    function checkWidth() {
        $placeHolder.toggle($window.width() >= 768);
    }

    // Clone at start - then hide it    
    $sideBarContent.clone(true).appendTo($placeHolder);

    // Bind event listener and do initial execute
    $window.resize(checkWidth).trigger("resize");
});

JSFiddle: http://jsfiddle.net/TrueBlueAussie/jtfv4jjt/6/

Again this can be shortened:

$(function () {
    var $window = $(window);
    var $sideBarContent = $('#sidebar .dummy-content');
    var $placeHolder = $('#place-holder');

    // Clone content at start - then hide it 
    $sideBarContent.clone(true).appendTo($placeHolder);

    // Bind event listener and do initial execute
    $window.resize(function(){
        $placeHolder.toggle($window.width() >= 768)
    }).trigger("resize");
});

JSFiddle: http://jsfiddle.net/TrueBlueAussie/jtfv4jjt/7/

That's all for now :)

One last point:

If you use Twitter bootstrap, you can simply decorate the panel with an appropriate class (something like visible-md ) and all this will happen for you :)

Answer 2

Take the event listener outside the document.ready() function:

$(document).ready(function(){
    ...
});

$(window).resize(checkWidth);

Also, take out the checkWidth() function outside the document.ready() function.