Security of user's Data in JavaScript.

Hi all, Here I would like to share one of my concerns about Javascript data security. I don't know how many of us really aware of the user's Data security in a JavaScript application. In my understanding, if we have some user data which we will store dynamically in variable as reference and it can be passwords, credit card numbers, other user confidential data. It will be available when the specific JavaScript function execute. So it means we can access those data in console. Doesn't it a less security? Please correct me and give an exact answer if I am wrong. I hope the question is clear.

Thanks!