是否有一种有效的方法来判断DOM元素(在HTML文档中)当前是否可见(出现在视口中)?
(这个问题指的是Firefox。)
是否有一种有效的方法来判断DOM元素(在HTML文档中)当前是否可见(出现在视口中)?
(这个问题指的是Firefox。)
当前回答
更新:时间在流逝,我们的浏览器也是如此。这种方法不再被推荐,如果你不需要支持ie7之前的版本,你应该使用Dan的解决方案。
原来的解决方案(现已过时):
这将检查元素是否在当前视口中完全可见:
function elementInViewport(el) {
var top = el.offsetTop;
var left = el.offsetLeft;
var width = el.offsetWidth;
var height = el.offsetHeight;
while(el.offsetParent) {
el = el.offsetParent;
top += el.offsetTop;
left += el.offsetLeft;
}
return (
top >= window.pageYOffset &&
left >= window.pageXOffset &&
(top + height) <= (window.pageYOffset + window.innerHeight) &&
(left + width) <= (window.pageXOffset + window.innerWidth)
);
}
你可以简单地修改它,以确定元素的任何部分在视口中是否可见:
function elementInViewport2(el) {
var top = el.offsetTop;
var left = el.offsetLeft;
var width = el.offsetWidth;
var height = el.offsetHeight;
while(el.offsetParent) {
el = el.offsetParent;
top += el.offsetTop;
left += el.offsetLeft;
}
return (
top < (window.pageYOffset + window.innerHeight) &&
left < (window.pageXOffset + window.innerWidth) &&
(top + height) > window.pageYOffset &&
(left + width) > window.pageXOffset
);
}
其他回答
这检查元素是否至少部分在视图中(垂直维度):
function inView(element) {
var box = element.getBoundingClientRect();
return inViewBox(box);
}
function inViewBox(box) {
return ((box.bottom < 0) || (box.top > getWindowSize().h)) ? false : true;
}
function getWindowSize() {
return { w: document.body.offsetWidth || document.documentElement.offsetWidth || window.innerWidth, h: document.body.offsetHeight || document.documentElement.offsetHeight || window.innerHeight}
}
作为Element.getBoundingClientRect()的支持,最简单的解决方案已经变得完美:
function isInView(el) {
const box = el.getBoundingClientRect();
return box.top < window.innerHeight && box.bottom >= 0;
}
/**
* Returns Element placement information in Viewport
* @link https://stackoverflow.com/a/70476497/2453148
*
* @typedef {object} ViewportInfo - Whether the element is…
* @property {boolean} isInViewport - fully or partially in the viewport
* @property {boolean} isPartiallyInViewport - partially in the viewport
* @property {boolean} isInsideViewport - fully inside viewport
* @property {boolean} isAroundViewport - completely covers the viewport
* @property {boolean} isOnEdge - intersects the edge of viewport
* @property {boolean} isOnTopEdge - intersects the top edge
* @property {boolean} isOnRightEdge - intersects the right edge
* @property {boolean} isOnBottomEdge - is intersects the bottom edge
* @property {boolean} isOnLeftEdge - is intersects the left edge
*
* @param el Element
* @return {Object} ViewportInfo
*/
function getElementViewportInfo(el) {
let result = {};
let rect = el.getBoundingClientRect();
let windowHeight = window.innerHeight || document.documentElement.clientHeight;
let windowWidth = window.innerWidth || document.documentElement.clientWidth;
let insideX = rect.left >= 0 && rect.left + rect.width <= windowWidth;
let insideY = rect.top >= 0 && rect.top + rect.height <= windowHeight;
result.isInsideViewport = insideX && insideY;
let aroundX = rect.left < 0 && rect.left + rect.width > windowWidth;
let aroundY = rect.top < 0 && rect.top + rect.height > windowHeight;
result.isAroundViewport = aroundX && aroundY;
let onTop = rect.top < 0 && rect.top + rect.height > 0;
let onRight = rect.left < windowWidth && rect.left + rect.width > windowWidth;
let onLeft = rect.left < 0 && rect.left + rect.width > 0;
let onBottom = rect.top < windowHeight && rect.top + rect.height > windowHeight;
let onY = insideY || aroundY || onTop || onBottom;
let onX = insideX || aroundX || onLeft || onRight;
result.isOnTopEdge = onTop && onX;
result.isOnRightEdge = onRight && onY;
result.isOnBottomEdge = onBottom && onX;
result.isOnLeftEdge = onLeft && onY;
result.isOnEdge = result.isOnLeftEdge || result.isOnRightEdge ||
result.isOnTopEdge || result.isOnBottomEdge;
let isInX =
insideX || aroundX || result.isOnLeftEdge || result.isOnRightEdge;
let isInY =
insideY || aroundY || result.isOnTopEdge || result.isOnBottomEdge;
result.isInViewport = isInX && isInY;
result.isPartiallyInViewport =
result.isInViewport && result.isOnEdge;
return result;
}
让我感到困扰的是,该功能没有以jquery为中心的版本可用。当我看到Dan的解决方案时,我发现有机会为那些喜欢用jQuery OO风格编程的人提供一些东西。它很漂亮,很时髦,对我来说很有魅力。
哒哒,哒哒,嘣
$.fn.inView = function(){
if(!this.length)
return false;
var rect = this.get(0).getBoundingClientRect();
return (
rect.top >= 0 &&
rect.left >= 0 &&
rect.bottom <= (window.innerHeight || document.documentElement.clientHeight) &&
rect.right <= (window.innerWidth || document.documentElement.clientWidth)
);
};
// Additional examples for other use cases
// Is true false whether an array of elements are all in view
$.fn.allInView = function(){
var all = [];
this.forEach(function(){
all.push( $(this).inView() );
});
return all.indexOf(false) === -1;
};
// Only the class elements in view
$('.some-class').filter(function(){
return $(this).inView();
});
// Only the class elements not in view
$('.some-class').filter(function(){
return !$(this).inView();
});
使用
$(window).on('scroll',function(){
if( $('footer').inView() ) {
// Do cool stuff
}
});
我的更短更快的版本:
function isElementOutViewport(el){
var rect = el.getBoundingClientRect();
return rect.bottom < 0 || rect.right < 0 || rect.left > window.innerWidth || rect.top > window.innerHeight;
}
和一个jsFiddle按要求:https://jsfiddle.net/on1g619L/1/