JSFiddle - React, Tailwind, and code Playground

JavaScript

var s='local->ethernet->port3->rx_flow',
    s2='q4234',
    a=s.split('->'),
    obj=constructObject(a, s2);

function constructObject(a, final) {
    var val=a.shift();
    var obj={};
    if (a.length>0) {
        obj[val]=constructObject(a, final);
    } else {
        obj[val]=final;
    }
    return obj;
}

alert(obj.local.ethernet.port3.rx_flow);