JSFiddle - React, Tailwind, and code Playground

JavaScript

var formArray = {
    "valueFromA0" : "7",
    "valueFromA1" : undefined,
    "valueFromB0" : "5",
    "valueFromB1" : undefined
};

function removeEmptyEntries(obj)
{
    for(var prop in obj)
    {
        if(obj.hasOwnProperty(prop) && !obj[prop])
            delete obj[prop];
    }
}


removeEmptyEntries(formArray);
console.log(formArray);