Javascript Per Cycle

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A JavaScript for loop executes a block of code as long as the specified condition is true. For JavaScript loops take three arguments: initialization, state and increment. The condition expression is evaluated on each loop. A loop continues to execute if the expression evaluates to true.

Loops repeat the same block of code until a certain condition is met. They are useful for many repetitive programming tasks.

For example, you can have two lists of first names, middle names, and last names , which you want to merge into one full name list. You can write one line of code for each name, but it could take hundreds of lines of code if the list is long. Also, if you are not sure how long the list will be? Here you can use a loop that repeats a block of similar code by joining each item in the list.

There are two main types of loops used in JavaScript:. while and for loops. While loops are condition-based and run as long as that condition equals true. For loops are executed a set of conditions given are true. They can count the number of iterations performed by the loop.

In this guide, we’ll explore the basics of JavaScript for loops. We’ll also discuss the for ... in and for ... JavaScript loops and use a few examples to illustrate how these loops work in JavaScript.

JavaScript for Loops

A for loop repeatedly executes the same code until a condition is met. Each iteration of a loop executes the same code with a different value. The syntax for an for loop is as follows:

This syntax is quite complex, so we’re going to break it down and define each term we used

Initialization <. / strong> allows you to declare a counter variable. This variable keeps track of how many times our loop has been executed

Condition is the condition that is evaluated before the start of each loop . If the state equals true, the code in the loop will be executed. If the condition becomes false, the loop will stop working

Increment Updates day of the counter loop each time the loop is executed.

Either using a basic example to show how for JavaScript works is a loop here that the number prints between 0 and 5:.

Our code returns the following:

You can see that our code has been running repeatedly until our loop condition is When the number 4 is printed on the, our loop stops. JavaScript console This is because we have asked our loop to print the digits in the range 0 and 5.

Components of a For loop in JavaScript

Let & rsquo ; s break down our example regarding the components of a for loop:


initialization of our loop declares a variable that keeps track of how many times our loop has been completed. In the example above, we used let i = 0 ;. This tells our program to start a counter called i which has the initial value 0.

initialization variables are usually named i., but you can use any variable name you want.


Our loop uses i < 5 condition. This tells our program that our loop should only work when the i variable is less than 5. If

i is equal to or greater than 5, our loop will stop.


At the end of our loop, our code uses i ++ as an increment. This function tells our program to add 1 i variables every time the loop is executed

For JavaScript Loop:. How

Now that we have broken our cycle, we can discuss how the cycle works as a whole. Here is the code for the loop we used above:

To begin with, we’ll declare an loop. This loop has an initialization variable set of 0. So our counter starts at 0.

So we say our loop should work when i is less than 5.

Our code i increments instead one each time our loop is executed. If our condition is met, the code in our loop is executed, which gives us the result we saw above. So our code iterates a block of code until i is five or greater, then our code breaks.

If we created a situation where our condition always returns true, the loop would become infinite. the infinite loops indefinitely continue unless the breakage statement added.

our code then prints i when the for statement is executed.

Note that each argument in a loop is optional. for example, if we have already declared an initialization variable, it is necessary to declare a new one. our loop Below is an example of a loop used with two arguments:. a condition and an increment

Our code returns:

We need to include the semicolon, even though we don’t have a specific ified initialization variable for our loop. This is because the semicolon is used to tell the program where the initialization, condition, and increment are displayed. Without a semicolon, JavaScript cannot interpret our loop.

JavaScript for ... In loops

... in loops can be used to Iterate elements in an iterable object. Here is the syntax for ... in loop in JavaScript:

... in loops are useful if one wants to execute a certain block of code depending on the number of attributes an object. For example, we could have a student object whose properties we want to print to the console.

Here is an example of a for… in loop that will cycle through each element in a student object. and print each attribute:

Our program returns the following:

As you can see, our program repeated each element in the student object and printed its property name. If we wanted to print the value of each item, we could use this code:

Our code returns the following:

We used the code from student [item] to get the value of each item in our iterable object. Next, we printed the item to the console using console.log ().

JavaScript For… Of Loops

For… in are useful when you want to iterate through the properties of an object. You should use a for… of if loop But if you want to iterate elements in an object.

We scroll through a series of students and write their names on the console:

Our code returns the following:

As you can See it, our for… of loop repeated each element in the students array. Each element is printed to the console.

The for ... loops de are more concise than a normal for loop. This makes a for ... of loop easier to read. The general rule for programming is to use the right tools for the job. For ... of loops are more easy to understand if you want to browse a list. So, do you should use ld for ... loops whenever possible.

Similarly , we can use for ... of on a string to iterate by its component characters. Here’s an example of this in action:

The result of our code is:

Our program repeated each letter of the name variable, then printed them individually to the console.

This can be useful if you want to check if a character appears in a string, for example.


For loops are a useful function in JavaScript that allows you to execute a block of code when a certain condition returns true.

In this article, we have seen how for loops work and how to use them in JavaScript. We also discussed the use of for… loops in and for… in in JavaScript. You are now ready to start automating repetitive tasks using for loops as JavaScript master !

👻 Read also: what is the best laptop for engineering students?

We hope this article has helped you to resolve the problem. Apart from Javascript Per Cycle, check other __main__ Python module-related topics.

Want to excel in Python? See our review of the best Python online courses 2023. If you are interested in Data Science, check also how to learn programming in R.

By the way, this material is also available in other languages:

Chen Lehnman

Munchen | 2023-01-27

array Python module is always a bit confusing 😭 Javascript Per Cycle is not the only problem I encountered. Checked yesterday, it works!

Manuel Ungerschaft

San Francisco | 2023-01-27

Maybe there are another answers? What Javascript Per Cycle exactly means?. I am just not quite sure it is the best method

Oliver Krasiko

Massachussetts | 2023-01-27

Simply put and clear. Thank you for sharing. Javascript Per Cycle and other issues with Loops was always my weak point 😁. Checked yesterday, it works!


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