To define the number of nodes in a node list, use the length property.
Example
You can try to run the following code to learn how to implement length property in JavaScript −
<!DOCTYPE html> <html> <body> <p>Demo Text1</p> <p id = "pid"></p> <script> var myLen = document.querySelectorAll("p"); document.getElementById("pid").innerHTML = "This document has " + myLen.length + " paragraph tags."; </script> </body> </html>