JSFiddle - React, Tailwind, and code Playground

by alexflav23

JavaScript

var x;

function isset(val) {
    var undefined;
    return val !== undefined;
};

// ReferenceError
try {
    console.log(isset(b));
} catch(e) {
    document.write(e)
}

console.log(isset(x));
console.log(isset(5));

function objectHasKey(obj, key) {
    var undefined;
    return obj[key] !== undefined;
};

var obj = {};
obj.exists = 5;

console.log(objectHasKey(obj, "exists"));
console.log(objectHasKey(obj, "does not exist"));