What are the three important manipulations done in a for loop on a loop variable

What are the three important manipulations done in a for loop on a loop variable?

2) Consider the following code snippet

function printArray(a)
  {
      var len = a.length, i = 0;
      if (len == 0)
         console.log("Empty Array");
      else
       {
          do
           {
              console.log(a[i]);
          }
 while (++i < len);
      }
 }

3) What will be the step of the interpreter in a jump statement when an exception is thrown?

4) What are the three important manipulations done in a for loop on a loop variable?

5) Consider the following code snippet

while (a != 0)
 {
    if (a == 1)
         continue;
    else
         a++;
 }