How can I submit value to javascript without submitting onclick

How can I submit an input value to a javascript function without submitting my onclick button? Here is the code:

I want to be able to submit the value to a javascript here is the code:

function myFunction() { var x = document.getElementById("demo").value;

Basically i want to submit my input value without having my submit button. Here is the code:

How can I submit my input without having a submit button?

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