How to Call a JS function using OnClick event [duplicate]

You are attempting to attach an event listener function before the element is loaded. Place fun() inside an onload event listener function. Call f1() within this function, as the onclick attribute will be ignored.

function f1() {
    alert("f1 called");
    //form validation that recalls the page showing with supplied inputs.    
}
window.onload = function() {
    document.getElementById("Save").onclick = function fun() {
        alert("hello");
        f1();
        //validation code to see State field is mandatory.  
    }
}

JSFiddle