how to log user inout using js code example

Example 1: How to save input from box html

function getInputFromTextBox() {
    var input = document.getElementById("userInput").value;
    alert(input);
}

Example 2: how to take input in javascript in coding

In JavaScript, we can get user input like this: 
var name = window.prompt("Enter your name: "); 
alert("Your name is " + name);