mouseup 之类的事件，鼠标移出窗口（或 iframe）时，释放点击，不会触发，除非事件绑定在 documentElement、document、window 上面。

例如：

window.addEventListener('mouseup', () => { console.log('on mouse up(window, capture)') }, true)
document.addEventListener('mouseup', () => { console.log('on mouse up(doc, capture)') }, true)
document.documentElement.addEventListener('mouseup', () => { console.log('on mouse up(html, capture)') }, true)
document.body.addEventListener('mouseup', () => { console.log('on mouse up(body, capture)') }, true)
window.addEventListener('mouseup', () => { console.log('on mouse up(window)') }, false)
document.addEventListener('mouseup', () => { console.log('on mouse up(doc)') }, false)
document.documentElement.addEventListener('mouseup', () => { console.log('on mouse up(html)') }, false)
document.body.addEventListener('mouseup', () => { console.log('on mouse up(body)') }, false)
  1. 当鼠标在页面中点击，然后直接释放点击时，控制台输出
on mouse up(window, capture)
on mouse up(doc, capture)
on mouse up(html, capture)
on mouse up(body, capture)
on mouse up(body)
on mouse up(html)
on mouse up(doc)
  1. 当鼠标在页面中点击，然后移动到窗口外释放点击时，控制台输出
on mouse up(window, capture)
on mouse up(doc, capture)
on mouse up(html, capture)
on mouse up(html)
on mouse up(doc)

该行为可能对自己实现一些 drag & drop 逻辑时有一定的影响。