1. For Loop

The for loop is used when you know in advance how many times the script should run.

Syntax

For (initialization, condition, increment)
{
Statements
}

Example

<script type="text/javascript">
var i=0;
for (i=0;i<=5;i++)
{
document.write("The number is " + i);
document.write("<br >");
}
</script>

2.While Loop

The  while loop loops through a block of code while a specified condition is true.

Syntax:

while (Condition)
  {
  repetitive statements
  }

Example:

<script type="text/javascript">
var i=0;
while (i<=5)
  {
  document.write("The number is " + i);
  document.write("<br >");
  i++;
  }
</script>

3.Do...while Loop

This loop will execute the block of code ONCE, and then it will repeat the loop as long as the specified condition is true.

Syntax

do
  {
 repetitive statements
  }
while (condition)

Example

<script type="text/javascript">
var i=0;
do
  {
  document.write("The number is " + i);
  document.write("<br>");
  i++;
  }
while (i<=5);
</script>

The break Statement

The break statement will break the loop and continue executing the code that follows after the loop (if any).
Example
<html>
<body>
<script type="text/javascript">
var i=0;
for (i=0;i<=10;i++)
  {
  if (i==3)
    {
    break;
    }
  document.write("The number is " + i);
  document.write("<br />");
  }
</script>
</body>
</html>

The continue Statement

The continue statement will break the current loop and continue with the next value.
Example
<html>
<body>
<script type="text/javascript">
var i=0
for (i=0;i<=10;i++)
  {
  if (i==3)
    {
    continue;
    }
  document.write("The number is " + i);
  document.write("<br >");
  }
</script>
</body>
</html>