JSFiddle - React, Tailwind, and code Playground

JavaScript

Object.defineProperty(Object.prototype, "toUpperCaseString", {
    value: function toUpperCaseString() {
        return this.toString().toUpperCase();
    },
    enumerable: false
});

for (var key in {}) {
    if (key === "toUpperCaseString") {
        console.log("I never print");
    }
}

console.log(({}).toUpperCaseString());