npm package: @stdlib/iter-step
Description: Create an iterator which returns a sequence of numbers according to a specified increment.
Author: The Stdlib Authors
Latest version: 0.2.3

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# iterStep

[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url] <!-- [![dependencies][dependencies-image]][dependencies-url] -->

> Create an iterator which returns a sequence of numbers according to a specified increment.

<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->

<section class="intro">

</section>

<!-- /.intro -->

<!-- Package usage documentation. -->

<section class="installation">

## Installation

```bash
npm install @stdlib/iter-step
```

</section>

<section class="usage">

## Usage

```javascript
var iterStep = require( '@stdlib/iter-step' );
```

#### iterStep( start, increment\[, N] )

Returns an iterator which returns a sequence of numbers according to a specified `increment`.

```javascript
var it = iterStep( 0, 2 );
// returns <Object>

var v = it.next().value;
// returns 0

v = it.next().value;
// returns 2

v = it.next().value;
// returns 4

// ...
```

The returned iterator protocol-compliant object has the following properties:

-   **next**: function which returns an iterator protocol-compliant object containing the next iterated value (if one exists) assigned to a `value` property and a `done` property having a `boolean` value indicating whether the iterator is finished.
-   **return**: function which closes an iterator and returns a single (optional) argument in an iterator protocol-compliant object.

By default, the function returns an infinite iterator (i.e., an iterator which never ends). To limit the number of returned values, provide a third argument.

```javascript
var it = iterStep( 0, 2, 3 );
// returns <Object>

var v = it.next().value;
// returns 0

v = it.next().value;
// returns 2

v = it.next().value;
// returns 4

var bool = it.next().done;
// returns true
```

</section>

<!-- /.usage -->

<!-- Package usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="notes">

## Notes

-   The returned iterator is guaranteed to return the `start` value. Beware, however, that values subsequent to the `start` value are subject to floating-point rounding errors. For example,

    ```javascript
    var it = iterStep( 0.1, 0.2 );
    // returns <Object>

    var v = it.next().value;
    // returns 0.1

    v = it.next().value;
    // returns ~0.3

    v = it.next().value;
    // returns 0.5
    ```

    If you desire more control over value precision, consider using [roundn][@stdlib/math/base/special/roundn]:

    ```javascript
    var roundn = require( '@stdlib/math-base-special-roundn' );
    var iterMap = require( '@stdlib/iter-map' );

    function round( v ) {
        return roundn( v, -2 );
    }

    // Create an iterator returning values subject to floating-point errors:
    var it1 = iterStep( 0.1, 0.2, 10 );

    // Create an iterator to round each value to the nearest hundredth:
    var it2 = iterMap( it1, roundn );

    // Perform manual iteration...
    var v;
    while ( true ) {
        v = it2.next();
        if ( v.done ) {
            break;
        }
        console.log( v.value );
    }
    ```

-   If an environment supports `Symbol.iterator`, the returned iterator is iterable.

</section>

<!-- /.notes -->

<!-- Package usage examples. -->

<section class="examples">

## Examples

<!-- eslint no-undef: "error" -->

```javascript
var iterStep = require( '@stdlib/iter-step' );

// Create an iterator which is subject to floating-point rounding errors:
var it = iterStep( 0.0, 0.02, 50 );

// Perform manual iteration...
var v;
while ( true ) {
    v = it.next();
    if ( v.done ) {
        break;
    }
    console.log( v.value );
}
```

</section>

<!-- /.examples -->

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<section class="references">

</section>

<!-- /.references -->

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<section class="related">

* * *

## See Also

-   <span class="package-name">[`@stdlib/array-from-iterator`][@stdlib/array/from-iterator]</span><span class="delimiter">: </span><span class="description">create (or fill) an array from an iterator.</span>
-   <span class="package-name">[`@stdlib/iter-datespace`][@stdlib/iter/datespace]</span><span class="delimiter">: </span><span class="description">create an iterator which returns evenly spaced dates over a specified interval.</span>
-   <span class="package-name">[`@stdlib/iter-incrspace`][@stdlib/iter/incrspace]</span><span class="delimiter">: </span><span class="description">create an iterator which returns evenly spaced numbers according to a specified increment.</span>
-   <span class="package-name">[`@stdlib/iter-linspace`][@stdlib/iter/linspace]</span><span class="delimiter">: </span><span class="description">create an iterator which returns evenly spaced numbers over a specified interval.</span>
-   <span class="package-name">[`@stdlib/iter-logspace`][@stdlib/iter/logspace]</span><span class="delimiter">: </span><span class="description">create an iterator which returns evenly spaced numbers on a log scale.</span>
-   <span class="package-name">[`@stdlib/iter-unitspace`][@stdlib/iter/unitspace]</span><span class="delimiter">: </span><span class="description">create an iterator which returns numbers incremented by one.</span>

</section>

<!-- /.related -->

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<section class="main-repo" >

* * *

## Notice

This package is part of [stdlib][stdlib], a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop [stdlib][stdlib], see the main project [repository][stdlib].

#### Community

[![Chat][chat-image]][chat-url]

---

## License

See [LICENSE][stdlib-license].


## Copyright

Copyright &copy; 2016-2026. The Stdlib [Authors][stdlib-authors].

</section>

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[@stdlib/array/from-iterator]: https://www.npmjs.com/package/@stdlib/array-from-iterator

[@stdlib/iter/datespace]: https://www.npmjs.com/package/@stdlib/iter-datespace

[@stdlib/iter/incrspace]: https://www.npmjs.com/package/@stdlib/iter-incrspace

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[@stdlib/iter/unitspace]: https://www.npmjs.com/package/@stdlib/iter-unitspace

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