我想在單擊 btn 時將樣式（特定背景顏色）的元素（跨度或 div）創建到父元素中？

Question

我想在單擊 btn 時將樣式（特定背景顏色）的元素（跨度或 div）創建到父元素中？

function openNav() {
document.getElementById("sidenav").style.width = "250px";
document.getElementById("main").style.marginLeft = "250px";
var body = document.getElementsByTagName("body")[0],
blackback = document.createElement("span"),
styleSpan = blackback.style.backgroundColor = "rgba(0,0,0,0.4)";
body.appendChild(styleSpan);
}

Answer 1

這一行是錯誤的： styleSpan = blackback.style.backgroundColor = "rgba(0,0,0,0.4)";

將樣式賦予 blackback 時不需要重新分配，並且需要將 blackback 傳遞給 appendChild 方法，因為這是您嘗試創建的元素。

試試這樣：

function openNav() {
  document.getElementById("sidenav").style.width = "250px";
  document.getElementById("main").style.marginLeft = "250px";
  var body = document.getElementsByTagName("body")[0];
  var blackback = document.createElement("span");
  blackback.style.backgroundColor = "rgba(0,0,0,0.4)";
  blackback.style.width= "250px";
  blackback.style.height= "250px";
  body.appendChild(blackback);
}