Loops execute a block of code a specified number of times, or while a specified condition is true.
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.
- 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.
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.
code to be executed
Note: The increment parameter could also be negative, and the <= could be any comparing statement.
Try it yourself »
document.write("The number is " + i);