@stdlib/string/to-grapheme-cluster-iterator/README.md

String manipulation functions.

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# graphemeClusters2iterator

> Create an iterator which iterates over [grapheme clusters][unicode-text-segmentation].

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## Usage

```javascript
var graphemeClusters2iterator = require( '@stdlib/string/to-grapheme-cluster-iterator' );
```

#### graphemeClusters2iterator( src\[, mapFcn\[, thisArg]] )

Returns an iterator which iterates over each [grapheme cluster][unicode-text-segmentation] in a `string`.

```javascript
var iter = graphemeClusters2iterator( '🌷🍕' );

var v = iter.next().value;
// returns '🌷'

v = iter.next().value;
// returns '🍕'

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

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.

To invoke a function for each `src` value, provide a callback function.

```javascript
function fcn( v ) {
    return v + v;
}

var it = graphemeClusters2iterator( 'beep', fcn );
// returns <Object>

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

v = it.next().value;
// returns 'ee'

v = it.next().value;
// returns 'ee'

// ...
```

The invoked function is provided three arguments:

-   **value**: [grapheme cluster][unicode-text-segmentation].
-   **index**: iterated value index.
-   **src**: source string.

```javascript
function fcn( v, i ) {
    return v + i;
}

var it = graphemeClusters2iterator( 'bar', fcn );
// returns <Object>

var v = it.next().value;
// returns 'b0'

v = it.next().value;
// returns 'a1'

v = it.next().value;
// returns 'r2'

// ...
```

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

```javascript
function fcn( v ) {
    this.count += 1;
    return v;
}

var ctx = {
    'count': 0
};

var it = graphemeClusters2iterator( '🌷🍕', fcn, ctx );
// returns <Object>

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

v = it.next().value;
// returns '🍕'

var count = ctx.count;
// returns 2
```

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## Notes

-   If an environment supports `Symbol.iterator`, the returned iterator is iterable.
-   In environments supporting `Symbol.iterator`, the function **explicitly** does **not** invoke a string's `@@iterator` method, regardless of whether this method is defined. To convert a string to an implementation defined iterator, invoke this method directly.

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## Examples

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

```javascript
var graphemeClusters2iterator = require( '@stdlib/string/to-grapheme-cluster-iterator' );

function repeat( str ) {
    return str + str;
}

// Create an iterator which iterates over grapheme clusters:
var it = graphemeClusters2iterator( 'Iñtërnâtiônàlizætiøn', repeat );

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

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* * *

## See Also

-   <span class="package-name">[`@stdlib/array/to-iterator`][@stdlib/array/to-iterator]</span><span class="delimiter">: </span><span class="description">create an iterator from an array-like object.</span>
-   <span class="package-name">[`@stdlib/string/to-grapheme-cluster-iterator-right`][@stdlib/string/to-grapheme-cluster-iterator-right]</span><span class="delimiter">: </span><span class="description">create an iterator which iterates from right to left over grapheme clusters.</span>

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[unicode-text-segmentation]: http://www.unicode.org/reports/tr29/

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

[@stdlib/string/to-grapheme-cluster-iterator-right]: https://github.com/stdlib-js/string/tree/main/to-grapheme-cluster-iterator-right

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</section>

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