@stdlib/string/for-each/README.md

String manipulation functions.

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# forEach

> Invokes a function for each character in a string.

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## Usage

```javascript
var forEach = require( '@stdlib/string/for-each' );
```

#### forEach( str, \[options,] clbk\[, thisArg ] )

Invokes a function for each character in a string.

```javascript
function log( value, index ) {
    console.log( '%d: %s', index, value );
}

forEach( 'Beep!', log );
/* =>
    0: B
    1: e
    2: e
    3: p
    4: !
*/
```

The invoked function is provided three arguments:

-   **value**: character.
-   **index**: starting character index.
-   **str**: input string.

To set the function execution context, provide a `thisArg`.

```javascript
function clbk() {
    this.count += 1;
}

var str = 'Hello, world!';

var ctx = {
    'count': 0
};

forEach( str, clbk, ctx );

var bool = ( str.length === ctx.count );
// returns true
```

The function supports the following options:

-   **mode**: type of characters over which to iterate. Must be one of the following:

    -   `'grapheme'`: grapheme clusters. Appropriate for strings containing visual characters which can span multiple Unicode code points (e.g., emoji).
    -   `'code_point'`: Unicode code points. Appropriate for strings containing visual characters which are comprised of more than one Unicode code unit (e.g., ideographic symbols and punctuation and mathematical alphanumerics).
    -   `'code_unit'`: UTF-16 code units. Appropriate for strings containing visual characters drawn from the basic multilingual plane (BMP) (e.g., common characters, such as those from the Latin, Greek, and Cyrillic alphabets).

    Default: `'grapheme'`.

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## Notes

-   By default, the function assumes the general case in which an input string may contain an arbitrary number of grapheme clusters. This assumption comes with a performance cost. Accordingly, if an input string is known to only contain visual characters of a particular type (e.g., only alphanumeric), one can achieve better performance by specifying the appropriate `mode` option.

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## Examples

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

```javascript
var forEach = require( '@stdlib/string/for-each' );

function log( value, index ) {
    console.log( '%d: %s', index, value );
}

forEach( 'presidential election', log );
forEach( 'Iñtërnâtiônàlizætiøn', log );
forEach( '🌷🍕', log );
forEach( '\uD834\uDD1E', log );
```

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* * *

## See Also

-   <span class="package-name">[`@stdlib/utils/for-each`][@stdlib/utils/for-each]</span><span class="delimiter">: </span><span class="description">invoke a function for each element in a collection.</span>

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[@stdlib/utils/for-each]: https://www.npmjs.com/package/@stdlib/utils-for-each

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