Async JavaScript Interview Question: Call Stack and Event Loop

🚨 JavaScript Async Interview Question What will be the output? async function test() { console.log("1"); setTimeout(() => { console.log("2"); }, 0); await Promise.resolve(); console.log("3"); } console.log("4"); test(); console.log("5"); This question tests understanding of: • Call Stack • Async/Await behavior • Microtask queue (Promises) • Macrotask queue (setTimeout) • JavaScript Event Loop Many developers get the order wrong the first time. What do you think the output will be? #JavaScript #FrontendInterview #AsyncJavaScript #EventLoop #ReactJS #FrontendDeveloper #ProductBasedCompany

🚨 JavaScript Interview Question What will be the output? function outer() { let count = 0; return function inner() { count++; console.log(count); }; } const fn1 = outer(); const fn2 = outer(); fn1(); fn1(); fn2(); fn2(); This question tests your understanding of: • Closures • Lexical scope • How JavaScript handles function instances Even though both functions come from the same outer() function, they behave independently. What do you think the output will be? #JavaScript #FrontendInterview #Closures #ReactJS #FrontendDeveloper #ProductBasedCompany

JavaScript Interview Question What will be the output? const obj1 = { name: "Suman" }; const obj2 = { name: "Suman" }; console.log(obj1 == obj2); console.log(obj1 === obj2); At first glance, many developers expect the result to be true because both objects have the same values. But JavaScript compares objects by reference, not by value. Even if two objects contain identical properties, they are stored in different memory locations. So what do you think the output will be? #JavaScript #FrontendInterview #ReactJS #FrontendDeveloper #FrontendArchitecture #ProductBasedCompany

🚨 JavaScript Interview Question What will be the output? const obj1 = { name: "Suman" }; const obj2 = { name: "Suman" }; console.log(obj1 == obj2); console.log(obj1 === obj2); At first glance, many developers expect the result to be true because both objects have the same values. But JavaScript compares objects by reference, not by value. Even if two objects contain identical properties, they are stored in different memory locations. So what do you think the output will be? #JavaScript #FrontendInterview #ReactJS #FrontendDeveloper #FrontendArchitecture #ProductBasedCompany

🚨 JavaScript Interview Question What will be the output? const obj = { name: "Frontend", greet: function () { console.log(this.name); } }; const greet = obj.greet; greet(); greet.call(obj); greet.bind(obj)(); This question tests understanding of: • this binding • call() • bind() • Function invocation context Many developers expect all three calls to behave the same. But JavaScript handles this differently depending on how the function is invoked. What do you think the output will be? #JavaScript #FrontendInterview #ReactJS #FrontendDeveloper #JavaScriptConcepts #ProductBasedCompany

🚨 JavaScript Interview Question What will be the output? const obj = { name: "Frontend", regularFunc: function () { console.log(this.name); }, arrowFunc: () => { console.log(this.name); } }; obj.regularFunc(); obj.arrowFunc(); Both functions are inside the same object. But the output is different. This question tests understanding of: • this binding • Arrow functions vs regular functions • Execution context in JavaScript Many developers assume both will print the same value. What do you think the output will be? #JavaScript #FrontendInterview #ReactJS #FrontendDeveloper #JavaScriptConcepts #ProductBasedCompany

🚨 JavaScript Interview Question What will be the output? const obj = { name: "Frontend", regularFunc: function () { console.log(this.name); }, arrowFunc: () => { console.log(this.name); } }; obj.regularFunc(); obj.arrowFunc(); Both functions are inside the same object. But the output is different. This question tests understanding of: • this binding • Arrow functions vs regular functions • Execution context in JavaScript Many developers assume both will print the same value. What do you think the output will be? #JavaScript #FrontendInterview #ReactJS #FrontendDeveloper #JavaScriptConcepts #ProductBasedCompany

🚨 JavaScript Async Interview Question What will be the output? console.log("Start"); setTimeout(() => { console.log("Timeout 1"); }, 0); Promise.resolve() .then(() => { console.log("Promise 1"); }) .then(() => { console.log("Promise 2"); }); setTimeout(() => { console.log("Timeout 2"); }, 0); console.log("End"); Looks simple… But many developers get the order wrong. Because JavaScript doesn’t execute async code the way we intuitively expect. This question tests your understanding of: • Call Stack • Microtask Queue • Macrotask Queue • JavaScript Event Loop What do you think the output will be? #JavaScript #FrontendInterview #EventLoop #ReactJS #FrontendDeveloper #ProductBasedCompany

🚨 JavaScript Async Interview Question What will be the output? function debounce(fn, delay) { let timer; return function (value) { clearTimeout(timer); timer = setTimeout(() => { fn(value); }, delay); }; } const log = debounce((v) => console.log(v), 100); log("A"); setTimeout(() => log("B"), 50); setTimeout(() => log("C"), 120); setTimeout(() => log("D"), 180); This question tests your understanding of: • Debounce behavior • setTimeout scheduling • How timers get cancelled and replaced • JavaScript async execution Many developers assume all values will print, but debounce changes the execution flow. What do you think the output will be? #JavaScript #FrontendInterview #Debounce #AsyncJavaScript #ReactJS #ProductBasedCompany

JavaScript Interview Question What will be the output? function outer() { let count = 0; return function inner() { count++; console.log(count); }; } const fn1 = outer(); const fn2 = outer(); fn1(); fn1(); fn2(); fn2(); This question tests your understanding of: • Closures • Lexical scope • How JavaScript handles function instances Even though both functions come from the same outer() function, they behave independently. What do you think the output will be? #JavaScript #FrontendInterview #Closures #ReactJS