为什么 append 不可能在两个 dom 元素中使用同一个子元素？

Question

I just notice I couldn't do

var d1 = document.createElement('div');
var d2 = document.createElement('div');
var p = document.createElement('p');

d1.appendChild(p); // d1 has p now
d2.appendChild(p); // d2 has p now
// but where is p in d1 ?

Some would say it's logic, but well, when I first noticed that I thought how uncool it was.

Why isn't that possible?

Answer 1

The DOM is a tree structure.

When you append an element, you change its parent.

A node, in the browser, is much more than just the text inside your P (that string could be shared, in fact). It also has a position, dimensions, a visibility, receives events that could have been fired in child elements, propagate events to its parent, and so on. Everything here depends on the position in the tree. Just like would many CSS selectors. It doesn't make a lot of sense to imagine it's the same element at two places, it's better to think about it as two nodes, with maybe some identical content.

If you want to have the same content at two places, you haveto clone it .

Answer 2

jQuery's appendTo() method inserts "every element in the set of matched elements to the end of the target". Try this:

p.appendTo(".div-class1, .div-class2")

Answer 3

for AppendChild same element multiple times, we can use this way:

//main function
function appendChildMultiple(parent) {
  //check function argument is an element
  if (parent.nodeType !== undefined) {
    const pTag = document.createElement("p");
    pTag.innerText = "This is the appended element";
    //finally append child to parent
    parent.appendChild(pTag);
  }
}

and:

// target the wrapper and create test elements
const wrapper = document.querySelector(".wrapper");
const d1 = document.createElement("div");
const d2 = document.createElement("div");
//append test elements to wrapper
wrapper.appendChild(d1);
wrapper.appendChild(d2);

//use appendChildMultiple function
appendChildMultiple(d1);
appendChildMultiple(d2);
//we appended "pTag" multiple times

if we use Functions, we can AppendChild same element multiple times whitout cloneNode

https://codepen.io/kiumad/pen/eYMNKYa