how to check empty input field in javascript code example

Example 1: how to make input field empty in javascript

Assuming the element you want to change has the id question, so you can do

document.getElementById("question").value = "";

Example 2: if input value is null do something

if(document.getElementById("question").value.length == 0)
{
    alert("empty")
}

Example 3: how to check if all inputs are not empty with javascript

const inputFeilds = document.querySelectorAll("input");

const validInputs = Array.from(inputFeilds).filter( input => input.value !== "");

console.log(validInputs) //[array with valid inputs]