How to check a input field is empty code example

Example 1: check if input is empty css

/* If input is not empty */
input:not(:placeholder-shown) {
  /* You need to add a placeholder to your fields. For example: <input "placeholder=" "/> */
  border-color: green;
}

/* If input is empty */
input:placeholder-shown {
  border-color: red;
}

Example 2: 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 = "";