元素焦点

• 获取focus元素

// Get the focused element:
var $focused = $(':focus');

// No jQuery:
var focused = document.activeElement;

// Does the element have focus:
var hasFocus = $('foo').is(':focus');

// No jQuery:
elem === elem.ownerDocument.activeElement;

• 使元素获得焦点 / 模糊焦点

focus()
blur()

原文：https://www.cnblogs.com/develon/p/11711272.html