The read-only isConnected property of the Node interface returns a boolean indicating whether the node is connected (directly or indirectly) to a Document object. 
 The read-only isConnected property of the Node interface returns a boolean indicating whether the node is connected (directly or indirectly) to a Document object. 
 A boolean value that is true if the node is connected to its relevant context object, and false if not. 
A standard DOM example:
js
let test = document.createElement("p"); console.log(test.isConnected); // Returns false document.body.appendChild(test); console.log(test.isConnected); // Returns true
A shadow DOM example:
js
// Create a shadow root const shadow = this.attachShadow({ mode: "open" }); // Create some CSS to apply to the shadow DOM const style = document.createElement("style"); console.log(style.isConnected); // returns false style.textContent = ` .wrapper { position: relative; } .info { font-size: 0.8rem; width: 200px; display: inline-block; border: 1px solid black; padding: 10px; background: white; border-radius: 10px; opacity: 0; transition: 0.6s all; positions: absolute; bottom: 20px; left: 10px; z-index: 3 } `; // Attach the created style element to the shadow DOM shadow.appendChild(style); console.log(style.isConnected); // Returns true
| Specification | 
|---|
| DOM Standard  # ref-for-dom-node-isconnected①  | 
| Desktop | Mobile | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chrome | Edge | Firefox | Internet Explorer | Opera | Safari | WebView Android | Chrome Android | Firefox for Android | Opera Android | Safari on IOS | Samsung Internet | |
isConnected | 
51 | 79 | 49 | No | 38 | 10 | 51 | 51 | 49 | 41 | 10 | 6.0 | 
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    https://developer.mozilla.org/en-US/docs/Web/API/Node/isConnected