html

<div class="btnNone">
    none情況下獲取Container寬度
</div>
<div class="btnBlock">
    block情況下獲取Container寬度
</div>

<div class="container none">
    <div class="item">
    </div>
</div>

css

    .container{
        width: 100%;
        height: 100%;
        background
 
: #FFFF80;
    }
    .block{
        display: block;
    }
    .none{
        display: none;
    }
    .item{
        height: 50%;
        width: 50%;
        background: #80FF80;
    }
    .btnNone,.btnBlock{
        width: 250px;
        height: 40px;
        font-size: 16px;
        background: #FF8080;
        color
 
: #ffffff;
        font-weight: bolder;
        text-align: center;
        line-height: 40px;
        margin: 20px;
        position: fixed;
        z-index: 99;
    }
    .btnBlock{
        top: 100px;
    }
    .btnNone{
        top:200px;
    }

js

(function ($) {


        $('.btnBlock').click(function
 
(){
            $('.container').removeClass('block').removeClass('none').addClass('block');
            alert($('.item').css('height'));
        })
        $('.btnNone').click(function(){
            $('.container').removeClass('none').removeClass('block').addClass('none');
            alert($('.item').css('height'));
        })
    })(jQuery)

初始狀態

none情況下獲取Container寬度

block情況下獲取Container寬度