How to pass variables from one page to another page in javascript

Hey,
I am new to javascript please help me how to pass the variables from one page to another page.

I have a login page with main.html in this page i have username and password. another page named as login.js file in this javascript file i have username array and password array.

When i login it works fine entering to welcome page up to here there was no problem but i am accessing to get the username and password to display in welcome screen.How to do this please help to do this.?

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