Loops are used to run
a piece of code
multiple times.
The code in a loop runs
repeatedly as long as
a certain condition
evaluates to true.
Let's look at the example given below,
where we print the numbers
from 1 to 5 using a for loop.
The steps followed while executing
the above for loop are as follows:
Step 1 -
Before execution of the loop,
the first statement,
let noOfRepeats = 1 is executed.
This creates a variable noOfRepeats
and
assigns the value 1 to it.
This step is only executed
once before the loop starts.
Step 2 -
The loop begins with
the evaluation of the second statement,
i.e., the condition noOfRepeats < 6.
The loop will only be executed,
if this condition evaluates to true
for each iteration of the loop.
Since the value of noOfRepeats
is currently 1,
the condition is true
and
the code block
of the loop is executed.
Each time the loop's
code block is executed,
it is known as an iteration.
If the code block
gets executed 7 times,
we can say that the loop
iterated 7 times.
Step 3 -
Once the code block is executed,
i.e., an iteration is completed,
the third statement, noOfRepeats++ gets executed.
and
the value of noOfRepeats
is incremented by 1.
Step 4 -
The loop then moves on
to the next iteration,
wherein it repeats
the steps from Step 2.
Steps 2, 3 and 4 are repeated
as long as the condition
in Step 2 evaluates to true.
If the condition evaluates to false,
the execution of the loop is stopped.
In the above example, at one point,
the value of noOfRepeats
will become 6 at Step 4.
Then as the next iteration
starts from Step 2,
the condition noOfRepeats < 6
would result to false
and
the execution of the loop
will be stopped.