sign up page for the multiple users using javascript

I want a sign-up page for multiple users in which when the user fills out the form and submits it then matches the data by email if the email is matched then match the password if the user is new then stores their data in local storage using an array and if the user exists in the array then alert to it welcome back in javascript and kindly code must be easy to understandable and the form contains only email password and submit button

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