js

for loop in javascript

In almost every programming language, the for loop is a very common and useful construct to iterate through data. A for loop is an excellent way to iterate over elements of arrays or other data sets in order.

JavaScript does not have many standard library functions, so most of what you see here can be used in any other language that supports the same syntax.

for loop in javascript

While there are other ways to achieve this, this tutorial will focus on using these types of loops. They may seem very basic at first glance, but it’s important to know them if you want to get as much out of your code as possible! Let’s take a look at all the different kinds of for loops JavaScript has to offer!

For Loop – for loop in javascript

A simple for loop is any for loop where the number of iterations is defined before the loop even starts. This can be done by setting the index and condition before the loop starts.

For example: In this example, we are defining the index to be i, and the condition is that i should be less than or equal to 10. This means that the loop will iterate from i being set to 0, to i being set to 9.

You can see this in the example in the console below. This type of for loop is incredibly useful for setting certain conditions for the number of times you want the loop to go through.

The only catch is that you need to know how to define what those variables are ahead of time!

code:

for (let i = 0; i < 10; i++){

console.log(i);

}

While Loop – for loop in javascript

A while loop is a type of loop that will keep looping while a given condition is met. The condition is checked at the beginning of each iteration.

This means that the loop will always execute at least once, even if the condition is false right away. This makes a while loop a good choice if you don’t know how many times you’ll want the loop to iterate.

For example: In this example, the loop will iterate while i is less than or equal to 10. You’ll notice that, even though i is 9 from the start, the loop still executes once.

This is because the condition is checked at the beginning of each iteration, meaning the loop will continue to iterate until i is 10. You can see this in the example below.

code:

var i=0;

while (i < 10){

console.log(i);

i++;

}

Nested For Loop – for loop in javascript

A nested for loop is where one for loop is placed inside another for loop. This is useful for iterating over different types of data at the same time.

For example, if you had an array of numbers and an array of strings, you could use one nested loop to iterate over the numbers and one nested loop to iterate over the strings.

For example: In this example, we have an array of numbers, an array of strings, and an array of objects. We then create two nested for loops.

The first loop iterates over the numbers, the second loops over the strings, and the third loop iterates over the objects.

If you take a look at the output below, you can see that each nested loop has executed once, which is what we wanted since we set the number of iterations to be 3.

code:

for (var x = 0; x < 10; x++) {

for (var y = 0; y < 10; y++){

console.log(“x: “ + x + “, y: “ + y);

}

}

Do-While Loop – for loop in javascript

A do-while loop is a type of loop that executes its code before checking the condition for the first time. While this may seem like a bad thing, it’s actually a great way to ensure that something happens at least once!

For example:

In this example, the do-while loop will execute its code first and then check the condition. This means that the loop will execute at least once, even if it is false from the start.

This is because the do-while loop executes its code before checking the condition. You can see this in the example below.

code:

var result = ;

var i = 0;

do {

i += 1;

result += i + ‘ ‘;

} while (i > 0 && i < 5);

For-Each Loop – for loop in javascript

A for-each loop is a special type of loop that iterates over every element in an array or data set.

For example:

In this example, the for-each loop iterates over every element in the numbers array. This is useful when you want to iterate over a large amount of data without needing to know the exact starting and ending positions of the data. You can see this in the example below.

code:

ForEach function:–

theArray.forEach(element => { // …use `element`… });

for-in loop:–

for (const propertyName in theArray) {

if (/*…is an array element property (see below)…*/)

{ const element = theArray[propertyName]; // …use `element`… }

}

for of loop:–

for (const element of theArray) { // …use `element`… }

Conclusion

For loops are one of the most basic and common functions in any programming language. In this article, we’ve covered all the different types of for loops that JavaScript has to offer.

These are great for looping through data or even with certain conditions set. Whether you’re new to programming or have some experience, you should understand these basic concepts.

They are the building blocks of almost every program you’ll ever write!

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