JSFiddle - React, Tailwind, and code Playground

JavaScript

// By attaching `t` to the prototype
function Speak1() {}
Speak1.prototype.t = 5;

// By attaching `t` to the newly created object
function Speak2() {
    this.t = 5;
}

// By returning an object containing `t` (thus overriding the formerly allocated this)
function Speak3() {
    return {
        t: 5
    };
}

console.log( (new Speak1()).t );
console.log( (new Speak2()).t );
console.log( (new Speak3()).t );