Chrome扩展工具提示文字（一个字）

Question

我想实现一个工具提示字典chrome扩展。当用户将鼠标悬停在文本上的一个块或一个单词上时，它将显示块选择或更改其背景颜色，并在单词下方显示工具提示。

我该如何实施？

我刚刚对background做过类似的事情：

core.js

// Unique ID for the className.
var MOUSE_VISITED_CLASSNAME = 'crx_mouse_visited';

// Previous dom, that we want to track, so we can remove the previous styling.
var prevDOM = null;

// Mouse listener for any move event on the current document.
document.addEventListener('mousemove', function (e) {
  var srcElement = e.srcElement;

  // Lets check if our underlying element is a DIV.
  if (srcElement.nodeName == 'DIV' || srcElement.nodeName == 'SPAN') {

    // For NPE checking, we check safely. We need to remove the class name
    // Since we will be styling the new one after.
    if (prevDOM != null) {
      prevDOM.classList.remove(MOUSE_VISITED_CLASSNAME);
    }

    // Add a visited class name to the element. So we can style it.
    srcElement.classList.add(MOUSE_VISITED_CLASSNAME);

    // The current element is now the previous. So we can remove the class
    // during the next iteration.
    prevDOM = srcElement;
  }
}, false);

core.css

.crx_mouse_visited {
  background-color: #bcd5eb !important;
  outline: 1px solid #5166bb !important;
}