JSFiddle - React, Tailwind, and code Playground

JavaScript

var setAge = function(newAge) {
    this.age = newAge;
};

var susan = new Object();
susan.age = 25;
susan.letMyAgeBe = setAge; //how the hell does this work?  
// here, update Susan's age to 35 using the method
susan.letMyAgeBe(35);

harry = new Object();
harry.iAmThisOld = setAge;
harry.iAmThisOld(55);

document.write("Susan: " + susan.age);
document.write("<br><br>");
document.write("Harry: " + harry.age);