Learn JavaScript
Loops
14.1
Lesson

for loop

Loops are used to run the same 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 - At the beginning of the loop, the first statement, let i = 1 executes, which creates a variable i and gives it a value of 1.

Step 2 - The loop then moves on to its first iteration. Here, the second statement, i < 6 is checked to see if it evaluates to true. Since the value of i is currently 1, the second statement is indeed true. The code block of the loop is then run.

Step 3 - The third statement, i++ finally executes at the end of this iteration, when everything inside the code block has been executed. Here, we increment the value of i 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 second statement evaluates to true. At one point, the value of i will be 6 at the beginning of an iteration, due to which the second statement,i < 6 will evaluate to false. At that point, the loop immediately terminates and no more code is run.