Tuesday, August 28, 2012

JavaScript For Loop

For Loops will execute a block of code a specified number of times.

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.


for (variable=startvalue;variable<endvalue;variable=variable+increment)
  code to be executed


The example below defines a loop that starts with i=0. The loop will continue to run as long as i is less than 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.


for (i=0; i<5; i++)
  x=x + "The number is " + i + "<br />";

Try it yourself »

The while loop

The while loop will be explained in the next chapter.

More Examples

Looping through HTML headings
Loop through the six different HTML headings.

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