JSFiddle - React, Tailwind, and code Playground

HTML

<form name="myForm" action="demo_form" method="post" onsubmit="return f1()">
    <button name="submit">submit</button>
</form>

JavaScript

x = 2;

function f1(){
    if(x == 1) {
        alert("Form could not be submited!");
        return false;
    }
    else if(x == 2) {
        return true;
    }
}