Seattle Programmer
Published in

Seattle Programmer

Programming with Loops

Loops are so Important in coding. Not only are they a basic logistical structure for computers. They also do allow you to create complex programs. Loops can make your code easier to read and edit because you know what is happening and where. Also, loops make coding more time-efficient: to code a program that initially contained loops without them. It would take you hours and hours to complete the same thing. But loops can differ between languages, and some do not support loops.

It is vital to understand differences in coding languages for many reasons. First, if coding is a serious career option for you, you will likely need to be proficient in multiple languages. It is practically mandatory to be a polyglot programmer if you want a senior programmer position anywhere. Also, all programming languages with loops; tend to be a required skill that is crucial to creating a complex program.

Let’s admit it, as a software engineer, you want to know multiple coding languages. Being a polyglot programmer leads to higher-level positions faster and allows for more job opportunities, increased employability, and expanding the toolbox you must solve problems in software programming. However, to compare the different languages, we need to understand loops by looking at three languages.


Python’s programming language has three loops: For loops, while loops, and nested loops.

A while loop repeats a series of codes based on if the condition of the statement remains true. The loop will not move to the following code block until the condition becomes false. Meaning, if you are not careful, you can create an infinite loop. This loop can be used to print a value a specified number of times, print a value counting until it reaches a specific number, or print a value increasing by a variable until it becomes a particular number.

Then there is the for loop. This loop is explicitly made to state items in a sequence. A sequence can be a list, dictionary, set, string, tuple, range, etc. A nested loop can be created by using a loop inside another loop. For example, a for loop inside a for loop, for loop inside a while loop, while loop inside a for loop, or a while loop inside a while loop.

This for loop print all the elements in the array “array_1.” The output is as follows.

2 4 78


Java has three different loops, two of which are very similar to Python’s loops. The first is a while loop. A while loop in Java also runs a specific code compilation if the statement’s condition is and remains valid. But, yet again, the loop will keep running until the statement’s condition renders false, just like a for loop in Python.

Then there is another for loop. In Java, a for loop is used as a while loop when you know how many times you want your loop to run. It does this by receiving three statements: a statement that is executed once, a condition, and a statement executed at the end of every iteration of the code block. With a for loop, you can create a for-each loop. This loop will run through items in an array, like the functions of a for loop in Python.

For loop example:

Lastly, there is a do-while loop. This loop is just like the while loop, except the interpreter only checks if the condition is valid after the code block has been run once. This means that the loop’s code lock will run at least once, even if the condition is false.


Unlike the previous two languages, JavaScript is a front-end programming language known as client-side programming. This kind of programming is responsible for the actual website the users will be interacting with and none of its data.

Even though it is a different type of language, JavaScript still has the for loop, while loop. For-while loop, along with infinite and nested loops. The For loop can be used to iterate its code a certain number of times, iterate through items in objects like an array, map, or set, or iterate specific properties of an object. A while loop contains a statement and will iterate through its code until the statement is false. And a do-while loop will run its code section then check if the statement is true or not. If it is true, it reruns the code; if not, the program exits the loop.

This block of code will execute then check the statement “i < 5” and continue to run until that statement is false.

Functional Programming

Now, what loops can achieve in programs are very significant. However, not all languages have loops. These languages are called functional programming languages. Functional programming is coding in functions rather than statements. These functions are pure; ones that, given the same input, have the same output, have no side effects[SR3]. And the solutions have very little physical meaning. In simpler terms, functional programming uses single-purpose, pure functions in sequence to solve nonphysical or mathematical problems.

These languages are beneficial since they are easy to read and debug. Pure functions and unchangeable data make the variables easy to identify. Because pure functions affect fewer factors, creating a smaller chance of making a bug; although, if there is a bug, it is easier to identify. Due to these characteristics, a pure function’s purpose is can typically be identified just by its name. For example, by reading the function “calc_circle_circumfrence” you know the function will calculate a circle’s circumference.

This is significant because it allows us to understand why there are no loops in these languages. Once you have entered a loop, a variable must change inside the loop for a loop to end. The program only enters a loop if the condition is true and leaves when the condition is false. And a loop can have any number of factors changed or affected because of it, making loops not pure, causing A functional programming language to not allow for loops. [SR4]

Just like object-oriented programming, there are many different functional programming languages. The most popular are Haskell, SML, Clojure, Scala, Erlang, Clean, F#, ML/OCaml Lisp / Scheme, XSLTSQL, and Mathematica. [SR5]

Loop Comparison

The most common loops in all coding languages are the for loop and the while loop. The syntax will differ between languages, as seen in Python, Java, and JavaScript examples. And even though Python and Java are both backend-programming languages, Java and JavaScript’s loops are more similar.

Even though Java and JavaScript have different sets of loops than Python, you can use the while loops in the same ways. It’s the For and do-while loops that differ. Java’s for loop has two functions, one to run through an array and one to iterate a program a specific number of times. In contrast, Python’s for loop runs through a sequence, like an array. However, you can use a while loop in Python to achieve the same function as a Java for loop. Setting the Python loop up with a condition that a new variable is less than or equal to the number of times you want to loop to iterate and in the code block, then adding one to that variable at the end of the code block.

Java script also has a third for loop function and the two that Java has. And as previously mentioned, this loop iterates through the enumerable properties of an object. Yet, Java and Python bit carry this function also using their loops. You can iterate through a map or dictionary in Java and Python, respectively, using a for loop, which is essentially the same thing as enumerable properties of an object.

The other clear difference is the go-while loop. Java and JavaScript both have this loop, while Python does not. To achieve the same results in Python, you would have to type the while loop code block twice, once before the loop (not as a loop at all), then in the loop after the condition statement. This programming strategy not only is a more extensive and messier amount of code, but it’s also more likely to contain bugs. If anything in your program changes, you must make sure both code blocks look the same, and it is human nature to miss something eventually.

Even though Python doesn’t have the do-while loop, you can still create nested loops with the other two. Same with Java and JavaScript but with all three loops. Also, because all three languages have a while loop that runs until the condition becomes false, you can create an infinite loop if your condition’s variables remain unchanging.

Recursion and loops

The primary function is to iterate over a set of code a known or unknown number of times. Even though we cannot use loops in a functional program, we can use recursion. Recursion repeats the call to a function n number of times. Here is an example:

In many ways, recursion is like a loop, and in programs that support both loops and recursion, you usually can supplement one for the other. However, there are some differences.

Recursion is also more expensive than loops in cost and memory, though recursion is easier to read and write than loops. Overall, it has less code than loops, takes less time to write, and read, and will have fewer potential bugs.


In the end, no one can learn every programing language ever created. First, there are thousands of different coding languages. Second, only a tiny handful are still in use today. Out of that handful, many types can achieve other things, like the differences between front-end and back-end coding, functional and object-oriented programming, and high- and low-level languages. For example, Python and Java alone cannot be used for front-end programming, while JavaScript’s entire purpose is for front-end coding. All three are considered high-level languages because they mimic English patterns and don’t deal directly with the hardware.

So, when given a software assignment, or when figuring out which languages are best suited to provide you with the skills you need for your career, it’s best to know the significance of each language, the ins and outs, and what the language can achieve in a program.



Get the Medium app

A button that says 'Download on the App Store', and if clicked it will lead you to the iOS App store
A button that says 'Get it on, Google Play', and if clicked it will lead you to the Google Play store