JSFiddle - React, Tailwind, and code Playground

JavaScript

function Example() { //There is no length property
    this.foo = 0.2;
    
    this.getFoo = function() {
        return foo;
    }
}

function ExampleTwo() {
    this.length = 0; //A public length property is provided
}


Object.defineProperty(Object.prototype, 'c', { //Demonstration with Object.prototype, showing potential caveats 
    get: function() {
        return this.length;
    }
});

alert(new Example().c); //Here, the c property returns undefined because Example has no length property!
alert(new ExampleTwo().c); //Yields 0