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
公认的答案对我不起作用。
2020年分解。
The (elem.offsetParent !== null) method works fine in Firefox but not in Chrome. In Chrome position: fixed will also make offsetParent return null even the element if visible in the page. User Phrogz conducted a large test (2,304 divs) on elements with varying properties to demonstrate the issue. https://stackoverflow.com/a/11639664/4481831 . Run it with multiple browsers to see the differences. Demo: //different results in Chrome and Firefox console.log(document.querySelector('#hidden1').offsetParent); //null Chrome & Firefox console.log(document.querySelector('#fixed1').offsetParent); //null in Chrome, not null in Firefox <div id="hidden1" style="display:none;"></div> <div id="fixed1" style="position:fixed;"></div> The (getComputedStyle(elem).display !== 'none') does not work because the element can be invisible because one of the parents display property is set to none, getComputedStyle will not catch that. Demo: var child1 = document.querySelector('#child1'); console.log(getComputedStyle(child1).display); //child will show "block" instead of "none" <div id="parent1" style="display:none;"> <div id="child1" style="display:block"></div> </div> The (elem.clientHeight !== 0). This method is not influenced by position: fixed and it also check if element parents are not-visible. But it has problems with simple elements that do not have a css layout and inline elements, see more here Demo: console.log(document.querySelector('#inline1').clientHeight); //zero console.log(document.querySelector('#div1').clientHeight); //not zero console.log(document.querySelector('#span1').clientHeight); //zero <div id="inline1" style="display:inline">test1 inline</div> <div id="div1">test2 div</div> <span id="span1">test3 span</span> The (elem.getClientRects().length !== 0) may seem to solve the problems of the previous 3 methods. However it has problems with elements that use CSS tricks (other then display: none) to hide in the page. Demo console.log(document.querySelector('#notvisible1').getClientRects().length); console.log(document.querySelector('#notvisible1').clientHeight); console.log(document.querySelector('#notvisible2').getClientRects().length); console.log(document.querySelector('#notvisible2').clientHeight); console.log(document.querySelector('#notvisible3').getClientRects().length); console.log(document.querySelector('#notvisible3').clientHeight); <div id="notvisible1" style="height:0; overflow:hidden; background-color:red;">not visible 1</div> <div id="notvisible2" style="visibility:hidden; background-color:yellow;">not visible 2</div> <div id="notvisible3" style="opacity:0; background-color:blue;">not visible 3</div>
结论。
所以我向你们展示的是没有什么方法是完美的。要进行适当的可见性检查，必须结合使用后3种方法。
其他回答
如果你对用户可见感兴趣:
function isVisible(elem) {
if (!(elem instanceof Element)) throw Error('DomUtil: elem is not an element.');
const style = getComputedStyle(elem);
if (style.display === 'none') return false;
if (style.visibility !== 'visible') return false;
if (style.opacity < 0.1) return false;
if (elem.offsetWidth + elem.offsetHeight + elem.getBoundingClientRect().height +
elem.getBoundingClientRect().width === 0) {
return false;
}
const elemCenter = {
x: elem.getBoundingClientRect().left + elem.offsetWidth / 2,
y: elem.getBoundingClientRect().top + elem.offsetHeight / 2
};
if (elemCenter.x < 0) return false;
if (elemCenter.x > (document.documentElement.clientWidth || window.innerWidth)) return false;
if (elemCenter.y < 0) return false;
if (elemCenter.y > (document.documentElement.clientHeight || window.innerHeight)) return false;
let pointContainer = document.elementFromPoint(elemCenter.x, elemCenter.y);
do {
if (pointContainer === elem) return true;
} while (pointContainer = pointContainer.parentNode);
return false;
}
测试对象(使用摩卡术语):
describe.only('visibility', function () {
let div, visible, notVisible, inViewport, leftOfViewport, rightOfViewport, aboveViewport,
belowViewport, notDisplayed, zeroOpacity, zIndex1, zIndex2;
before(() => {
div = document.createElement('div');
document.querySelector('body').appendChild(div);
div.appendChild(visible = document.createElement('div'));
visible.style = 'border: 1px solid black; margin: 5px; display: inline-block;';
visible.textContent = 'visible';
div.appendChild(inViewport = visible.cloneNode(false));
inViewport.textContent = 'inViewport';
div.appendChild(notDisplayed = visible.cloneNode(false));
notDisplayed.style.display = 'none';
notDisplayed.textContent = 'notDisplayed';
div.appendChild(notVisible = visible.cloneNode(false));
notVisible.style.visibility = 'hidden';
notVisible.textContent = 'notVisible';
div.appendChild(leftOfViewport = visible.cloneNode(false));
leftOfViewport.style.position = 'absolute';
leftOfViewport.style.right = '100000px';
leftOfViewport.textContent = 'leftOfViewport';
div.appendChild(rightOfViewport = leftOfViewport.cloneNode(false));
rightOfViewport.style.right = '0';
rightOfViewport.style.left = '100000px';
rightOfViewport.textContent = 'rightOfViewport';
div.appendChild(aboveViewport = leftOfViewport.cloneNode(false));
aboveViewport.style.right = '0';
aboveViewport.style.bottom = '100000px';
aboveViewport.textContent = 'aboveViewport';
div.appendChild(belowViewport = leftOfViewport.cloneNode(false));
belowViewport.style.right = '0';
belowViewport.style.top = '100000px';
belowViewport.textContent = 'belowViewport';
div.appendChild(zeroOpacity = visible.cloneNode(false));
zeroOpacity.textContent = 'zeroOpacity';
zeroOpacity.style.opacity = '0';
div.appendChild(zIndex1 = visible.cloneNode(false));
zIndex1.textContent = 'zIndex1';
zIndex1.style.position = 'absolute';
zIndex1.style.left = zIndex1.style.top = zIndex1.style.width = zIndex1.style.height = '100px';
zIndex1.style.zIndex = '1';
div.appendChild(zIndex2 = zIndex1.cloneNode(false));
zIndex2.textContent = 'zIndex2';
zIndex2.style.left = zIndex2.style.top = '90px';
zIndex2.style.width = zIndex2.style.height = '120px';
zIndex2.style.backgroundColor = 'red';
zIndex2.style.zIndex = '2';
});
after(() => {
div.parentNode.removeChild(div);
});
it('isVisible = true', () => {
expect(isVisible(div)).to.be.true;
expect(isVisible(visible)).to.be.true;
expect(isVisible(inViewport)).to.be.true;
expect(isVisible(zIndex2)).to.be.true;
});
it('isVisible = false', () => {
expect(isVisible(notDisplayed)).to.be.false;
expect(isVisible(notVisible)).to.be.false;
expect(isVisible(document.createElement('div'))).to.be.false;
expect(isVisible(zIndex1)).to.be.false;
expect(isVisible(zeroOpacity)).to.be.false;
expect(isVisible(leftOfViewport)).to.be.false;
expect(isVisible(rightOfViewport)).to.be.false;
expect(isVisible(aboveViewport)).to.be.false;
expect(isVisible(belowViewport)).to.be.false;
});
});
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。
const isVisible = (selector) => { let selectedElement let topElement let selectedData selectedElement = document.querySelector(selector) if (!selectedElement) { return false } selectedData = selectedElement.getBoundingClientRect() if (!selectedData || !Object.keys(selectedData)) { return false } if (!(selectedData.width > 0) || !(selectedData.height > 0)) { return false } topElement = document.elementFromPoint(selectedData.top, selectedData.left) if (selectedElement !== topElement) { return false } return true } const output = document.querySelector('.text') output.innerHTML = '.x element is visible: ' + isVisible('.x') .block { width: 100px; height: 100px; background: black; } .y { background: red; margin-top: -100px; } <div class="text"></div> <div class="x block"></div> <div class="y block"></div>
公认的答案对我不起作用。
2020年分解。
The (elem.offsetParent !== null) method works fine in Firefox but not in Chrome. In Chrome position: fixed will also make offsetParent return null even the element if visible in the page. User Phrogz conducted a large test (2,304 divs) on elements with varying properties to demonstrate the issue. https://stackoverflow.com/a/11639664/4481831 . Run it with multiple browsers to see the differences. Demo: //different results in Chrome and Firefox console.log(document.querySelector('#hidden1').offsetParent); //null Chrome & Firefox console.log(document.querySelector('#fixed1').offsetParent); //null in Chrome, not null in Firefox <div id="hidden1" style="display:none;"></div> <div id="fixed1" style="position:fixed;"></div> The (getComputedStyle(elem).display !== 'none') does not work because the element can be invisible because one of the parents display property is set to none, getComputedStyle will not catch that. Demo: var child1 = document.querySelector('#child1'); console.log(getComputedStyle(child1).display); //child will show "block" instead of "none" <div id="parent1" style="display:none;"> <div id="child1" style="display:block"></div> </div> The (elem.clientHeight !== 0). This method is not influenced by position: fixed and it also check if element parents are not-visible. But it has problems with simple elements that do not have a css layout and inline elements, see more here Demo: console.log(document.querySelector('#inline1').clientHeight); //zero console.log(document.querySelector('#div1').clientHeight); //not zero console.log(document.querySelector('#span1').clientHeight); //zero <div id="inline1" style="display:inline">test1 inline</div> <div id="div1">test2 div</div> <span id="span1">test3 span</span> The (elem.getClientRects().length !== 0) may seem to solve the problems of the previous 3 methods. However it has problems with elements that use CSS tricks (other then display: none) to hide in the page. Demo console.log(document.querySelector('#notvisible1').getClientRects().length); console.log(document.querySelector('#notvisible1').clientHeight); console.log(document.querySelector('#notvisible2').getClientRects().length); console.log(document.querySelector('#notvisible2').clientHeight); console.log(document.querySelector('#notvisible3').getClientRects().length); console.log(document.querySelector('#notvisible3').clientHeight); <div id="notvisible1" style="height:0; overflow:hidden; background-color:red;">not visible 1</div> <div id="notvisible2" style="visibility:hidden; background-color:yellow;">not visible 2</div> <div id="notvisible3" style="opacity:0; background-color:blue;">not visible 3</div>
结论。
所以我向你们展示的是没有什么方法是完美的。要进行适当的可见性检查，必须结合使用后3种方法。
所以我找到了最可行的方法:
function visible(elm) {
if(!elm.offsetHeight && !elm.offsetWidth) { return false; }
if(getComputedStyle(elm).visibility === 'hidden') { return false; }
return true;
}
这是基于以下事实:
显示:所有元素(即使是嵌套的元素)都没有宽度和高度。 可见性即使对于嵌套的元素也是隐藏的。
因此不需要测试offsetParent或在DOM树中循环来测试哪个父对象具有可见性:hidden。这应该可以在ie9中工作。
你可能会说，如果透明度:0和折叠的元素(有宽度但没有高度-反之亦然)也不是真正可见的。但话说回来，它们并不是隐藏的。
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