Parts of a While Loop

There are many different kinds of loops, but they all essentially do the same thing: they repeat an action some number of times.

Three main pieces of information that any loop should have are:

1. When to start: The code that sets up the loop — defining the starting value of a variable for instance.
2. When to stop: The logical condition to test whether the loop should continue.
3. How to get to the next item: The incrementing or decrementing step — for example, x = x * 3 or x = x - 1

Here's a basic while loop example that includes all three parts.

var start = 0; // when to start
while (start < 10) { // when to stop
  console.log(start);
  start = start + 2; // how to get to the next item
}

Prints:
0
2
4
6
8

If a loop is missing any of these three things, then you might find yourself in trouble. For instance, a missing stop condition can result in a loop that never ends!

Directions:

Write awhileloop that:

• Loop through the numbers 1 to 20
• If the number is divisible by 3, print "Julia"
• If the number is divisible by 5, print "James"
• If the number is divisible by 3 and 5, print "JuliaJames"
• If the number is not divisible by 3 or 5, print the number

/*
 * Programming Quiz: JuliaJames (4-1)
 */

var num = 1;
while (num <= 20) {
  if ( num % 3 === 0 && num % 5 === 0 ) {
      console.log("JuliaJames");
  } else if ( num % 3 === 0 ) {
      console.log("Julia");
  } else if ( num % 5 === 0 ) {
      console.log("James");
  } else {
        console.log( num );
  }
  num = num + 1;
}