NodeList.length
 The NodeList.length property returns the number of items in a NodeList. 
Syntax
numItems = nodeList.length
-  
numItemsis an integer value representing the number of items in aNodeList. 
Example
 The length property is often useful in DOM programming. It's often used to test the length of a list, to see if it exists at all. It's also commonly used as the iterator in a for loop, as in this example. 
// All the paragraphs in the document const items = document.getElementsByTagName("p"); // For each item in the list, // append the entire element as a string of HTML let gross = ""; for (let i = 0; i < items.length; i++) { gross += items[i].innerHTML; } // gross is now all the HTML for the paragraphs
Specifications
| Specification | 
|---|
| DOM Standard (DOM) # ref-for-dom-nodelist-length①  | 
Browser compatibility
| Desktop | Mobile | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chrome | Edge | Firefox | Internet Explorer | Opera | Safari | WebView Android | Chrome Android | Firefox for Android | Opera Android | Safari on IOS | Samsung Internet | |
length | 
1  | 
12  | 
1  | 
5  | 
Yes  | 
1  | 
Yes  | 
Yes  | 
4  | 
Yes  | 
1  | 
Yes  | 
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    https://developer.mozilla.org/en-US/docs/Web/API/NodeList/length