Looping

Loops are a way of repeating the same block of code over and over. There are two types of commands for looping. For and While.

While :
A while loop repeats a block of code while a condition is true. Like an if statement, the condition is found in parentheses.

Example :
var a = 1;
while (a < 10) {
    alert(a);
    a = a+ 1;
}
// i is now 10

For  :
A for loop is similar to an if statement, but it combines three semicolon-separated pieces information between the parentheses: initialization, condition and a final expression.

The initialization part is for creating a variable to let you track how far through the loop you are - like i in the while example; the condition is where the looping logic goes - the same as the condition in the while example; and the final expression is run at the end of every loop.

Example:
for (var z = 1; z < 10; z++) {
    alert(z);
}
This gives us alert boxes containing the numbers 1 to 10 in order.

By the way, z++ is equivalent to z = z + 1