Input condition is wrong

[tskxz]

No description provided.

[tskxz]

The problem is the boolean values are inverse, we need to fix it by changing it return true to return 0 and vice versa return false to return 1

function validateInput() {
    var username = document.getElementById('username').value;
    var regex = /^[a-zA-Z0-9]+$/;
    if (!regex.test(username)) {
        alert('Invalid username. Only alphanumeric characters are allowed.');
         return true;
    }
     return false;
}

To

function validateInput() {
    var username = document.getElementById('username').value;
    var regex = /^[a-zA-Z0-9]+$/;
    if (!regex.test(username)) {
        alert('Invalid username. Only alphanumeric characters are allowed.');
         return 0;
    }
     return 1;
}