Introduction to Loops

Repetition

The repetition of an instruction or a group of instructions is a commonly encountered phenomenon in programming called a loop. As an example, say we want our program to perform the following tasks:

• To read a document or data file line by line repeatedly until the end of the file.

• To draw an image pixel by pixel repeatedly using color values that show it on the screen.

• To iterate through a collection of variables one by one to process its values.

• To compute a result by applying a formula to several values.

The for–of loop

Let’s say we want to display integers from $0$ to $4$. We can simply display the numbers $0$ to $4$ one by one using the console.log() statement. We can also use one variable and log its value repeatedly by changing the value of the variable, as shown below:

The code above clearly shows the repetitive use of console.log(a);. The benefit of using a single variable is that we can convert this repetition into a for loop. In JavaScript, we use a ...