Call Nested function in Nodejs

How to call the nested isPasswordValid() function in users.js from test.js file

users.js

'use strict';
var zxcvbn = require('zxcvbn'),
httpStatus = require('http-status-codes');

module.exports = function (users) {
function isPasswordValid(password) {
var passwordValidatorResult = zxcvbn(password);
console.log('score: ', passwordValidatorResult.score);
//if score is less than 3 then reject the user creation request
if (passwordValidatorResult.score < 3) {
return passwordValidatorResult.feedback;
} else {
return true;
}
}
}  

test.js

var user = require('./users.js');


var res = user().isPasswordValid('234fdsf');
// Not working
if(var == true)
{
console.log('Valid');
} else {
console.log('Invalid');
}

How to call nested function isPasswordValid nd

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