JSFiddle - React, Tailwind, and code Playground

JavaScript

var deleted = {
        a: 1
    };
    
    var cleared = {
        a: 1
    };
    window.ppp = "sddsds";
    delete deleted["a"];
    cleared["a"] = undefined;
    
    for(var key in deleted) {
        console.log("deleted has key", key);
    }
    
    for(var key in cleared) {
        console.log("cleared has key", key);
    }
    
    console.log("deleted has a?", deleted.hasOwnProperty('a'));
    console.log("cleared has a?", cleared.hasOwnProperty('a'));

    delete window.pop;
    console.log(window.pop);