Learn the Importance of JavaScript for Loop

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In this article, we will look at JavaScript for loop and the structures that can help you quickly complete repetitive tasks, from sets of calculations to other situations in which you must work with similar items.

What Is JavaScript for Loop?

JS for loop is crucial to programming as it involves doing the same thing repeatedly, also known as iteration. Using the for loop usually involves several features, which can include a few things:

  • A counter: The value that tells the loop where and when to start.
  • A condition to exit: The criteria that tell the JavaScript for loop when it should stop. This usually happens when the counter has reached the predetermined value.
  • An iterator: Determines how often the counter moves in increments.

With every iteration of the JavaScript for loop, you can check if the proper amount has been reached yet. If so, then the loop can be exited. If not, the loop will run through again.

Why JavaScript for Loop Is Vital 

A loop is good for completing a repetitive task or, because the code can be different in each loop’s iteration, tasks that are similar — like calculations. A JavaScript for loop can significantly shorten the amount of time that it would take to complete a task. 

JavaScript for Loop Construction 

Most JavaScript bootcamps will teach you the importance of constructing a loop. The one that you will use most often is the for loop, which looks something like this:

In this loop, we have the keyword, which is “for.” We also have the initializer, the exit condition and the final condition. The curly brackets will contain the code that will run each time the JavaScript for loop is run.

In any for loop, you want to ensure you have incremented or decremented the initializer so it can reach the condition to exit. If you do not allow the loop to reach the exit condition, then the loop can keep going forever — or until your browser crashes.

Exiting a JavaScript for Loop

At some point during your work, you might need to exit the JS for loop before the iteration has completed. If so, use a break statement, which causes the JavaScript for loop to immediately stop, allowing the browser to continue on to the next code.

For example, if you want to search an array that contains telephone numbers, your code would look something like this:

To create the JavaScript for loop, define the variable with each piece of contact information. Then, place the event listener, which allows the code to run when you press the button.

To run this type of  loop, use zero to start your counter and run it until it is equal to or greater than the contacts.length. You can then increment by one after each of the loop’s iterations. Splitting the contact allows you to store these values as splitContact. You can plug in your conditional statement to determine whether the name of the contact equaled the search. If so, you can place a string in your paragraph to say what the number of the contact and end the loop with “break.”

If this process does not return a contact name, you can set the text to report “Contact was not found” and set the loop to continue until the condition to exit the JavaScript for loop is met.

Types of JavaScript Loops

A JavaScript bootcamp might also teach you that even though for is the most common type of JavaScript loop, do…while and while loops can also be useful, since they can be used fairly interchangeably to solve similar problems. The one that you choose to use will depend on the one you like the best or the one that is easiest for you to use.

Let’s look at each of these types of JavaScript loops. The first one is for. To use it, use this code:

The next JavaScript loop is while. This is very similar to a for loop. However, in this type of JavaScript loop, you set the initializer before you set the loop. The last expression will be inside your loop after your code to run. This is different from the for loop, which requires the two items to be inside of a parenthesis. The condition for exiting the loop is inside of the parenthesis. This is the code to run this type of loop:

The last application of a JavaScript loop is do…while. While it is very similar to the while code., there is one difference between the two: the exit condition comes at the very end, preceded by the keyword “while.” The code for this looks like the following:

When you are just starting out, you may want to stick to using the JavaScript loop for, since it is most likely going to be the easiest loop to remember. Because for is simpler, you will be more likely to remember the condition to exit, final expression and initializer. Additionally, because each of these must be placed in parentheses, you will be better able to look at each one and make sure they are in place before testing your JS for loop coding.

There are some other types of features and loops better suited for more advanced or specialized situations. Reading a guide about loops and an iteration can help you learn more about JavaScript loops.

Closing Thoughts

Now, you should know more about why using a JavaScript for loop is an excellent way of working with long code. Whether or not you pursue a JavaScript bootcamp in San Francisco or elsewhere, this tutorial can help you prepare.

*Please note, these articles are for educational purposes and the topics covered may not be representative of the curriculum covered in our boot camp. Explore our curriculum to see what you’ll learn in our program.

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