使用JS，是否有某种方法可以检测哪些文本可以在浏览器窗口中查看？

Question

使用jQuery，我用

选择div中的所有文本

var c = $('#content').text();

但我想只选择浏览器窗口中正在查看的文本。所以，只是澄清我的想法的一个粗略的例子，看看下面的图像：

应该只返回：

  

自行车车架是自行车的主要部件，其上有车轮和其他车辆

然而，如果我要打开浏览器，并重新运行代码

  

自行车车架是自行车的主要部件，车轮和其他部件安装在自行车车架上。直立式自行车的现代和最常见的框架设计基于安全自行车，由两个三角形组成，一个主三角形和一个成对的后三角形。这被称为钻石框架。1框架需要坚固，坚硬和轻盈，它们通过组合不同的材料和形状来实现。

应该退回。

是否有某种方法可以检测浏览器窗口中任何给定时刻哪些文本可见？

Answer 1

是的，您需要测量视口以计算元素顶部的距离。请参阅此fiddle。

$.fn.is_on_screen = function(){

    var win = $(window);

    var viewport = {
        top : win.scrollTop(),
        left : win.scrollLeft()
    };
    viewport.right = viewport.left + win.width();
    viewport.bottom = viewport.top + win.height();

    var bounds = this.offset();
    bounds.right = bounds.left + this.outerWidth();
    bounds.bottom = bounds.top + this.outerHeight();

    return (!(viewport.right < bounds.left || viewport.left > bounds.right || viewport.bottom < bounds.top || viewport.top > bounds.bottom));

};

if( $('.target').length > 0 ) { // if target element exists in DOM
    if( $('.target').is_on_screen() ) { // if target element is visible on screen after DOM loaded
        $('.log').html('<div class="alert alert-success">target element is visible on screen</div>'); // log info       
    } else {
        $('.log').html('<div class="alert">target element is not visible on screen</div>'); // log info
    }
}
$(window).scroll(function(){ // bind window scroll event
    if( $('.target').length > 0 ) { // if target element exists in DOM
        if( $('.target').is_on_screen() ) { // if target element is visible on screen after DOM loaded
            $('.log').html('<div class="alert alert-success">target element is visible on screen</div>'); // log info
        } else {
            $('.log').html('<div class="alert">target element is not visible on screen</div>'); // log info
        }
    }
});

<强> HTML

<div class="log">log</div>

scroll to target element<br> scroll to target element<br> scroll to target element<br> scroll to target element<br>
scroll to target element<br> scroll to target element<br> scroll to target element<br> scroll to target element<br>
scroll to target element<br> scroll to target element<br> scroll to target element<br> scroll to target element<br>
scroll to target element<br> scroll to target element<br> scroll to target element<br> scroll to target element<br>
scroll to target element<br> scroll to target element<br> scroll to target element<br> scroll to target element<br>
scroll to target element<br> scroll to target element<br> scroll to target element<br> scroll to target element<br>
scroll to target element<br> scroll to target element<br> scroll to target element<br> scroll to target element<br>
scroll to target element<br> scroll to target element<br> scroll to target element<br> scroll to target element<br>
scroll to target element<br> scroll to target element<br> scroll to target element<br> scroll to target element<br>
scroll to target element<br> scroll to target element<br> scroll to target element<br> scroll to target element<br>
scroll to target element<br> scroll to target element<br> scroll to target element<br> scroll to target element<br>
scroll to target element<br> scroll to target element<br> scroll to target element<br> scroll to target element<br>
scroll to target element<br> scroll to target element<br> scroll to target element<br> scroll to target element<br>
scroll to target element<br> scroll to target element<br> scroll to target element<br> scroll to target element<br>
scroll to target element<br> scroll to target element<br> scroll to target element<br> scroll to target element<br>
scroll to target element<br> scroll to target element<br> scroll to target element<br> scroll to target element<br>


<div class="target label label-info">target element</div>


scroll to target element<br> scroll to target element<br> scroll to target element<br> scroll to target element<br>
scroll to target element<br> scroll to target element<br> scroll to target element<br> scroll to target element<br>
scroll to target element<br> scroll to target element<br> scroll to target element<br> scroll to target element<br>
scroll to target element<br> scroll to target element<br> scroll to target element<br> scroll to target element<br>
scroll to target element<br> scroll to target element<br> scroll to target element<br> scroll to target element<br>

<强> CSS

.log {
    position: fixed;
    right: 20px;
    top: 20px;
}

Answer 2

我认为：visible伪选择器可以帮助我们。

$('<div/>').html( $('.selector') ).contents().filter(':visible').text();