While

While Loops repetitively execute a block of code as long as a specified condition is true.

while (condition) {
  // do it as long as condition is true
}

For example, the loop in this example will repetitively execute its block of code as long as the variable i is less than 5:

var i = 0,
  x = "";
while (i < 5) {
  x = x + "The number is " + i;
  i++;
}

Note: Be careful to avoid infinite looping if the condition is always true!