html<ul id = "user-list">  <li>張三</li>  <li>李四</li>  <li>王五</li>  <li>趙六</li></ul>jslet list = document.querySelector("#user-list")let items = document.querySelectorAll("#user-list > li")list.addEventListener('click', function(e) {    if(e.target.tagName === "LI") {  //請問這2行怎么理解？      let item = e.target        items.forEach(function(item) {        item.style.background = "inherit"      item.style.color = "inherit"    })        item.style.background = "black"    item.style.color = "white"        console.log(item.innerHTML)  }})