有什么方法,我可以检查如果一个元素是可见的纯JS(没有jQuery) ?
因此,给定一个DOM元素,我如何检查它是否可见?我试着:
window.getComputedStyle(my_element)['display']);
但这似乎并不奏效。我想知道我应该检查哪些属性。我想到了:
display !== 'none'
visibility !== 'hidden'
还有我可能漏掉的吗?
有什么方法,我可以检查如果一个元素是可见的纯JS(没有jQuery) ?
因此,给定一个DOM元素,我如何检查它是否可见?我试着:
window.getComputedStyle(my_element)['display']);
但这似乎并不奏效。我想知道我应该检查哪些属性。我想到了:
display !== 'none'
visibility !== 'hidden'
还有我可能漏掉的吗?
当前回答
我有一个更有效的解决方案相比AlexZ的getComputedStyle()解决方案时,有位置“固定”元素,如果一个愿意忽略一些边缘情况(检查评论):
function isVisible(el) {
/* offsetParent would be null if display 'none' is set.
However Chrome, IE and MS Edge returns offsetParent as null for elements
with CSS position 'fixed'. So check whether the dimensions are zero.
This check would be inaccurate if position is 'fixed' AND dimensions were
intentionally set to zero. But..it is good enough for most cases.*/
return Boolean(el.offsetParent || el.offsetWidth || el.offsetHeight);
}
附注:严格来说,“可见性”首先需要定义。在我的情况下,我正在考虑一个元素可见,只要我可以运行所有DOM方法/属性上没有问题(即使不透明度为0或CSS可见性属性是“隐藏”等)。
其他回答
结合上面的几个答案:
function isVisible (ele) {
var style = window.getComputedStyle(ele);
return style.width !== "0" &&
style.height !== "0" &&
style.opacity !== "0" &&
style.display!=='none' &&
style.visibility!== 'hidden';
}
就像AlexZ说的,这可能会比你的一些其他选择更慢,如果你更具体地知道你在寻找什么,但这应该抓住所有隐藏元素的主要方式。
但是,这也取决于你认为什么是可见的。例如,一个div的高度可以设置为0px,但内容仍然可见,这取决于溢出属性。或者,可以将div的内容设置为与背景相同的颜色,这样用户就不会看到它,但仍然可以在页面上显示。或者一个div可以移出屏幕或隐藏在其他div后面,或者它的内容可以是不可见的,但边界仍然可见。在一定程度上,“可见”是一个主观术语。
Chrome 105(以及Edge和Opera)和Firefox 106引入了element . checkvisibility(),如果元素是可见的,则返回true,否则返回false。
该函数检查了使元素不可见的各种因素,包括display:none、可见性、内容可见性和不透明度:
let element = document.getElementById("myIcon");
let isVisible = element.checkVisibility({
checkOpacity: true, // Check CSS opacity property too
checkVisibilityCSS: true // Check CSS visibility property too
});
旁注:checkVisibility()以前被称为isVisible()。看这个GitHub问题。 参见这里的checkVisibility()规范草案。
如果我们只是收集检测能见度的基本方法,让我不要忘记:
opacity > 0.01; // probably more like .1 to actually be visible, but YMMV
至于如何获取属性:
element.getAttribute(attributename);
所以,在你的例子中:
document.getElementById('snDealsPanel').getAttribute('visibility');
But wha? It doesn't work here. Look closer and you'll find that visibility is being updated not as an attribute on the element, but using the style property. This is one of many problems with trying to do what you're doing. Among others: you can't guarantee that there's actually something to see in an element, just because its visibility, display, and opacity all have the correct values. It still might lack content, or it might lack a height and width. Another object might obscure it. For more detail, a quick Google search reveals this, and even includes a library to try solving the problem. (YMMV)
看看下面的问题,它们可能是这个问题的副本,有很好的答案,包括来自强大的约翰·雷西格的一些见解。但是,您的特定用例与标准用例略有不同,因此我将避免标记:
如何判断一个DOM元素是否在当前视口中可见? 如何检查一个元素是否真的可见javascript?
(EDIT: OP SAYS HE'S SCRAPING PAGES, NOT CREATING THEM, SO BELOW ISN'T APPLICABLE) A better option? Bind the visibility of elements to model properties and always make visibility contingent on that model, much as Angular does with ng-show. You can do that using any tool you want: Angular, plain JS, whatever. Better still, you can change the DOM implementation over time, but you'll always be able to read state from the model, instead of the DOM. Reading your truth from the DOM is Bad. And slow. Much better to check the model, and trust in your implementation to ensure that the DOM state reflects the model. (And use automated testing to confirm that assumption.)
根据MDN文档,元素的offsetParent属性将在它或它的任何父元素通过display style属性被隐藏时返回null。只要确保元素不是固定的。一个脚本来检查这个,如果你没有位置:fixed;页面上的元素可能是这样的:
// Where el is the DOM element you'd like to test for visibility
function isHidden(el) {
return (el.offsetParent === null)
}
另一方面,如果您确实有位置固定的元素可能会在此搜索中被捕获,那么您将不得不遗憾地(并且缓慢地)使用window.getComputedStyle()。这种情况下的函数可能是:
// Where el is the DOM element you'd like to test for visibility
function isHidden(el) {
var style = window.getComputedStyle(el);
return (style.display === 'none')
}
选项2可能更简单一点,因为它考虑了更多的边缘情况,但我打赌它也会慢很多,所以如果你不得不多次重复这个操作,最好避免它。
使用与jQuery相同的代码:
jQuery.expr.pseudos.visible = function( elem ) {
return !!( elem.offsetWidth || elem.offsetHeight || elem.getClientRects().length );
};
在函数中:
function isVisible(e) {
return !!( e.offsetWidth || e.offsetHeight || e.getClientRects().length );
}
在我的Win/IE10、Linux/Firefox中工作得很好。45岁的Linux / Chrome.52……
感谢没有jQuery的jQuery!