What is the output of the following? “`js class Animal { constructor(name) { this.name = name; } speak() { return `${this.name} makes a noise.`; } } class Dog extends Animal { speak() { return `${this.name} barks.`; } } const d = new Dog(‘Rex’); console.log(d.speak()); console.log(d instanceof Animal); “` JavaScript DeveloperHard Try Now
What is tail call optimization and which JavaScript syntax enables it in strict mode? JavaScript DeveloperHard Try Now
What is the output of the following? “`js const handler = { get(target, key) { return key in target ? target[key] : 37; } }; const p = new Proxy({a: 1}, handler); console.log(p.a, p.b); “` JavaScript DeveloperHard Try Now
What is the output of the following? “`js console.log(1 + ‘2’ + 3); console.log(1 + 2 + ‘3’); “` JavaScript DeveloperHard Try Now
What is the correct way to implement a custom iterable in JavaScript? JavaScript DeveloperHard Try Now
What is the output of the following? “`js function foo() { ‘use strict’; console.log(this); } foo(); “` JavaScript DeveloperHard Try Now
What is the output of the following? “`js const sym = Symbol(‘key’); const obj = { [sym]: 42, name: ‘test’ }; console.log(Object.keys(obj)); “` JavaScript DeveloperHard Try Now
What is the difference between microtasks and macrotasks in the JavaScript event loop? JavaScript DeveloperHard Try Now
What is the output of the following? “`js let x = 1; function foo(x, y = x * 2) { return y; } console.log(foo(3)); “` JavaScript DeveloperHard Try Now
What is the output of the following? “`js const p1 = Promise.resolve(1); const p2 = Promise.reject(new Error(‘fail’)); const p3 = Promise.resolve(3); Promise.allSettled([p1, p2, p3]).then(results => { console.log(results.length); }); “` JavaScript DeveloperHard Try Now
What is the output of the following? “`js const a = [1, 2]; const b = [1, 2]; console.log(a == b, a === b); “` JavaScript DeveloperHard Try Now
What is the output of the following? “`js async function foo() { return 1; } async function bar() { return await foo(); } bar().then(console.log); “` JavaScript DeveloperHard Try Now
