This content originally appeared on DEV Community and was authored by Adrian Matei
I would definitely put the following question in an interview, if am interested in knowing if the candidate knows a bit about the Javascript runtime.
What is the order in which the following texts are logged via console.log?
console.log('1 - start');
setTimeout(() => console.log('2 - setTimeout1'), 0);
Promise.resolve('Success')
.then(()=> console.log('3 - promise1'))
.then(()=> console.log('4 - promise2'));
setTimeout(() => console.log('5 - setTimeout2'), 0);
console.log('6 - end');
If you are not sure about the answer read this In depth: Microtasks and the JavaScript runtime environment article before
Output
1 - start// statement is executed directly in the script (first "Run script" task)
5 - end // part of the first "Run script" task gets executed too
3 - promise1 // placed in microTasks queue and executed between tasks, after first "Run script" task is ready
4 - promise2 // microtask added during previous microtask execution and executed immediately
2 - setTimeout1 // callback execution scheduled in another task in the "macroTasks" queue (also task queue), executed in the next interation of the event-loop
5 - setTimeout2 // callback execution scheduled in another task in the task queue, executed in the next iteration of event-loop
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This content originally appeared on DEV Community and was authored by Adrian Matei
Adrian Matei | Sciencx (2021-08-14T18:56:59+00:00) Javascript runtime interview question. Retrieved from https://www.scien.cx/2021/08/14/javascript-runtime-interview-question/
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