javascript - Why does a for loop with a semicolon after it still execute?

Question

I was having a look at some code a friend did and stumbled across this line which I thought was an error (simplified for example)..

for (g = 0; 10 > g; g++); {

    alert(g);
}

However it still executes, and alerts "10". Why is this? Is this a purpose built function in javascript?

JS fiddle

Answer 1

Your g variable is within the global context, so it is accessible outside of a for loop. The loop did its job, and incremented g 10 times.
Two {} indicate a block in JavaScript and won't cause any error.

Edit: it is not alerting anything without a for loop, because the g variable is not defined.