JavaScript array iteration - MDN example

Question

I was reading the re-introduction to JavaScript on the MDN website and came across this example in the Array section:

for (var i = 0, item; item = a[i++];){
   // Do something with item
}

Where "a[]" is an array being looped over.

I am confused about the value that "item" will have in its first iteration. As i=0 and item is at first undefined, then when it is assigned the value of a[i++] wouldn't the iteration start from i=1, which would mean that the iteration would start from the second element in the a[] array -> a[1], skipping over the first element a[0] entirely?

Answer 1

i++ is the post increment operator, which means that it increments i by 1 but evaluates to the old (non-incremented) value.

> i = 0
  0
> i++
  0
> i
  1