How to put a limit on the index of an array in a loop?

Question

JavaScript

there is an array
p = [....];
There is such a code

for(b=0;b<p.length;b++){
  var y = p[b];
  if(y <= ?? && y > 0){
    d++
  }
}

If I put just p[1] then it will check it with the value corresponding to this
index

Answer 1

determine the desired index, and put it instead of p.length in the loop condition

Answer 2

Write in the condition a restriction not on the value of the array cell, but on the index. That is, if( b <= 1 )