JavaScript For Loop

This page explains the "for" loop, and why it's different to the "while" loop.

We learned in the previous lesson that "loops" enable your program to continuously execute a block of code for a given number of times, or while a given condition is true.

In that lesson, we saw that the While loop executes code while a condition is true.

In this lesson, we will see that the JavaScript For loop executes code for a specified number of times.

Therefore, we could rewrite the example from the previous lesson to use a for loop.

Example For statement:

<script>
var myBankBalance = 0;
var msg = "";
for (myBankBalance = 0; myBankBalance <= 10; myBankBalance++) {
  msg = msg + "My bank balance is $" + myBankBalance + "<br>";
}
document.write(msg);
</script>

Exlanation of code

We started by declaring a variable called myBankBalance and setting it to 0.
We then opened a for loop with our condition between brackets.

Our condition sets a value to our variable, checks if the current value of the variable is less than or equal to 10, then increments the value by 1.
This is followed by code to execute while the condition is true.

In this case, we are simply, outputting the current value of myBankBalance, preceded by some text. This code is placed within curly braces.
When the browser reaches the closing curly brace, if the condition is still true, it goes back to the first curly brace and executes the code again.

Of course, by now, the myBankBalance variable has been incremented by 1. If the condition is not true (i.e. the variable is greater than 10), it exits from the loop.