The answer would be Option 2: 55555 because

var i;
for (i = 0; i &lt; 5; i++) { ... }

Loop will run from 0 to 4 but will break when i will be 5.
setTimeout will schedule 5 callbacks which will run after at least 10 secs.
Since, i is defined in the outer scope, its value will be overwritten on each iteration and final value will be 5.
When callbacks are executed, they will get the final value of i i.e. 5.

To capture each value of i in the respective callbacks, there are two popular solutions to the question.

for (let i = 0; i &lt; 5; i++) {
    setTimeout(function() {
        console.log(i);
    }, 10);
}

for (var i = 0; i &lt; 5; i++) {
    setTimeout(function(i) {
        return function() { console.log(i); }
    }(i), 10);
}

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