从 iFrame 中获取 BoundingClientRect

Question

我有一个函数可以评估元素（iFrame）是否在视口内（如果元素在视图中）returns true。

function isElementInViewport() {
    var el = document.getElementById('postbid_if')
    var rect = el.getBoundingClientRect();
    var elemTop = rect.top;
    var elemBottom = rect.bottom;

    console.log("eleTom " + elemTop)
    console.log("elemBottom " + elemBottom)
    console.log("window.innerHeight " + (window.innerHeight + (window.top.innerHeight * 0.5)))

    var isVisible = (elemTop >= 0) && (elemBottom <= (window.innerHeight + window.innerHeight * 0.5));
    return isVisible;
}

此函数直接在页面上提供时可以正常工作，但在实时环境中运行此函数时它位于 iFrame 内，看起来 getBoundingClientRect() 引用的是 iFrame 的视口而不是主 window?

有什么方法可以在带有 getBoundingClientRect()

的 iFrame 中使用主 window 视口

Answer 1

每个 iframe 都有自己的作用域，因此 iframe 中的 window 不同于 root window.

您可以通过 window.top 获得根目录 window 并且利用这些知识您可以计算当前 iframe 的绝对位置。这是一个正确的函数：

function currentFrameAbsolutePosition() {
  let currentWindow = window;
  let currentParentWindow;
  let positions = [];
  let rect;

  while (currentWindow !== window.top) {
    currentParentWindow = currentWindow.parent;
    for (let idx = 0; idx < currentParentWindow.frames.length; idx++)
      if (currentParentWindow.frames[idx] === currentWindow) {
        for (let frameElement of currentParentWindow.document.getElementsByTagName('iframe')) {
          if (frameElement.contentWindow === currentWindow) {
            rect = frameElement.getBoundingClientRect();
            positions.push({x: rect.x, y: rect.y});
          }
        }
        currentWindow = currentParentWindow;
        break;
      }
  }
  return positions.reduce((accumulator, currentValue) => {
    return {
      x: accumulator.x + currentValue.x,
      y: accumulator.y + currentValue.y
    };
  }, { x: 0, y: 0 });
}

现在在 isElementInViewport 中更改这些行：

var elemTop = rect.top;
var elemBottom = rect.bottom;

至

var currentFramePosition = getCurrentFrameAbsolutePosition();
var elemTop = rect.top + currentFramePosition.y;
var elemBottom = rect.bottom + currentFramePosition.y;

这应该有效。

Answer 2

下面是跨域 iframe 的代码：

window.addEventListener('message', async (event) => {
  if (event.data.channel !== GET_IFRAME_COORDINATES_MESSAGE) return;

  const coordinates = window === window.top
    ? { x: 0, y: 0 }
    : await getFrameCoordinates();

  const iframes = document.getElementsByTagName('iframe');
  for (const iframe of iframes) {
    if (iframe.src !== event.data.href) continue;
    const { x, y } = iframe.getBoundingClientRect();
    event.source.postMessage({
      channel: `${GET_IFRAME_COORDINATES_MESSAGE}-reply`,
      coordinates: {
        x: coordinates.x + x,
        y: coordinates.y + y,
      }
    }, '*');
    break;
  }
});

async function getFrameCoordinates() {
  return new Promise((resolve, reject) => {
    const listenForFrameCoordinatesResponse = (event) => {
      if (event.data.channel !== `${GET_IFRAME_COORDINATES_MESSAGE}-reply`) return;
      window.removeEventListener('message', listenForFrameCoordinatesResponse);
      resolve(event.data.coordinates);
    };
    window.addEventListener('message', listenForFrameCoordinatesResponse);
    window.parent.postMessage({
      channel: GET_IFRAME_COORDINATES_MESSAGE,
      href: window.location.href,
    }, '*');
    setTimeout(() => reject(new Error('Getting frame coordinates timeout')), 2000);
  });
}

从 iFrame 中获取 BoundingClientRect

getBoundingClientRect from within iFrame

javascript

iframe

cross-domain

getboundingclientrect