90 % of Javascript Developer fail to answer these code snippets (Asked in Interview) Part-1

Vineet Mishra
2 min readFeb 15, 2022

Q1. Guess the output?

let x = true
setTimeout (()=>{
x= false
})

while (x)
{
console.log(“hello”)
}

Take a deep breath don’t jump into the solution, think hard

Output:

Hello

Hello ….will go on printing

Reason: In this case, the value of x is true in the global scope and as we know that javascript is a single thread language, the setTimeout is an asynchronous operation so it will go in the task queue and wait for its chance for execution so now we go to “while loop “ the value of x is true so it satisfies the given condition in the while loop now it will print continuously “hello” and after 2 seconds the setTimeout is ready for execution but the call stack is not empty, it is already running the while loop so setTimeout will not get any chance of execution

Q2 Guess the ouput?

let x = true
let count =0;

setTimeout(()=>{
x= false;
},2000)

setInterval(()=>{
if(x)
{
console.log(count++)
}
},200)

Take a deep breath don’t jump into the solution, think hard

Output:

0
1
2
3
4
5
6
7
8

the cursor will be not free on the output screen

Reason:In this case, the setTimeout and setInterval is an asynchronous operations so first, it calls the setInterval
,setInterval will print the value of count every 200 milliseconds and then after 2-second setTimeout
will invoke and setInterval condition get dissatisfied, it will print up to 8 and execution will continue

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Vineet Mishra

Full Stack Developer at CCR Tech, I write about Mobile/Web Development and Deployment, and Interview Q & A