JSFiddle - React, Tailwind, and code Playground

JavaScript

function funcX(A,B,C){        
    if(typeof A != 'string'){A= "A"}
    if(typeof B != 'string'){B= "B"}
    if(typeof C != 'string'){C= "C"}

    alert(A+B+C)
};
funcX(null, null, 'c');