JavaScript For Loop
Loops execute a block of code
a specified number of times, or while a specified condition is true.
JavaScript Loops
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
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
5. 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.
Example
<html>
<body>
<script type="text/javascript">
var i=0;
for (i=0;i<=5;i++)
{
document.write("The number is " + i);
document.write("<br />");
}
</script>
</body>
</html> |
Try it yourself »
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The while loop
The while loop will be explained in the next chapter.
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More Examples |
Looping through HTML headings
Loop through the six different HTML headings.
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