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Loops in JavaScript are used to execute the
same block of code a specified number of times or while a
specified condition is true.
JavaScript Loops
Very often when you write code, you want the same block of
code to run over and over again in a row. Instead of adding
several almost equal lines in a script we can use loops to
perform a task like this.
In JavaScript there are two different kind of loops:
- for - loops through a block of code a specified
number of times
- while - loops through a block of code while a
specified condition is true
The for Loop
The for loop is used when you know in advance how many times
the script should run.
Syntax
for (var=startvalue;var<=endvalue;var=var+increment)
{
code to be executed
}
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Example
Explanation: The example below defines a loop that starts
with i=0. The loop will continue to run as long as i is
less than, or equal to 10. i will increase by 1 each time
the loop runs.
Note: The increment parameter could also be negative,
and the <= could be any comparing statement.
<html>
<body>
<script type="text/javascript">
var i=0
for (i=0;i<=10;i++)
{
document.write("The number is " + i)
document.write("<br />")
}
</script>
</body>
</html>
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Result
The number is 0
The number is 1
The number is 2
The number is 3
The number is 4
The number is 5
The number is 6
The number is 7
The number is 8
The number is 9
The number is 10
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The while loop
The while loop will be explained in the next chapter. |
