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by MaratJanuary 26th, 2023

There are situations, when during the development of an application, there is a need to create a sequence of data, such as a sequence of numbers that can serve as identifiers.

Some programming languages have special built-in `range`

functions that can generate such data, but JavaScript does not.

In this article, we will look at how to implement a similar function in JavaScript and how to use it in different situations.

The `range`

function in JavaScript can be useful in cases where you need to generate a sequence of integers or other data types with a certain amount of spacing between values. Also, as an example, you can give a sequence of dates, with an interval of a day, a week, or a month.

However, let’s begin with an easier example and use the `range`

function to generate a sequence of numbers from 1 to 10 like this:

```
range(1, 10); // [1, 2, 3, ..., 10]
```

Below you can see one of the implementations of the range function to generate a sequence of numbers:

```
function range(start, end) {
const seq = [];
for (let i = start; i <= end; i++) {
seq.push(i);
}
return seq;
}
```

In this example above, the `range`

function creates a new array `seq`

and fills it with integers using a `for`

loop. After the array is filled, the function returns it.

You can change the step between elements of a sequence by adding a third argument to the function:

```
function range(start, end, step) {
const seq = [];
for (let i = start; i <= end; i += step) {
seq.push(i);
}
return seq;
}
range(1, 10, 2); // [1, 3, 5, 7, 9]
```

Here, the `range`

function returns an array of odd numbers from 1 to 10 since the initial value is set to 1 and the step is set to 2. You can also change the direction of the sequence generation by specifying a negative step like this:

```
function range(start, end, step) {
const seq = [];
for (let i = start; i >= end; i += step) {
seq.push(i);
}
return seq;
}
range(10, 1, -2); // [10, 8, 6, 4, 2]
```

Note that the `range`

function only works with integers. If you need to generate a sequence of fractional numbers, then you need to write an appropriate function or use other ways to generate a sequence with fractional numbers.

The `range`

function can be used to create a sequence of strings, such as a sequence of letters from the alphabet:

```
function range(start, end, step = 1) {
const start = start.charCodeAt(0);
const end = end.charCodeAt(0);
const seq = [];
for (let i = start; i <= end; i += step) {
seq.push(String.fromCharCode(i));
}
return seq;
}
range('a', 'z'); // ['a', 'b', 'c', ..., 'z']
```

In this example, we initiate the `charCodeAt`

method on the start and end value of the sequence. The `charCodeAt`

method returns the numeric value for the character at the specified index.

Next, using the `for`

loop, iterate over the elements of the sequence and set the values using the `String.fromCharCode()`

method. The static method `String.fromCharCode()`

returns a string created from the specified character code. After the array is filled, the function returns it.

In the previous examples, the `range`

function generates either a sequence of integers or strings from start to end values with a given step. However, you can also create a `range`

function with more complex logic that will work on different data types at the same time.

To summarize, we have analyzed the `range`

function in JavaScript, which allows you to generate a sequence of numbers and strings with a certain step.

We learned how to implement such a function with a `for`

loop and how to use it in various situations. Use the `range`

function to simplify your code and speed up development.

L O A D I N G

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