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# gjoinBetween

> Return a string by joining strided array elements using a specified separator for each pair of consecutive elements.

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## Usage

```javascript
var gjoinBetween = require( '@stdlib/blas/ext/base/gjoin-between' );
```

#### gjoinBetween( N, prefix, suffix, x, strideX, separators, strideS )

Returns a string by joining strided array elements using a specified separator for each pair of consecutive elements.

```javascript
var x = [ 1, 2, 3, 4 ];
var sep = [ ' + ', ' - ', ' != ' ];

var str = gjoinBetween( x.length, 'op: ', '', x, 1, sep, 1 );
// returns 'op: 1 + 2 - 3 != 4'
```

The function has the following parameters:

-   **N**: number of indexed elements.
-   **prefix**: string to prepend to the output string.
-   **suffix**: string to append to the output string.
-   **x**: input array.
-   **strideX**: stride length for `x`.
-   **separators**: separators array.
-   **strideS**: stride length for `separators`.

The `N` and stride parameters determine which elements in the strided arrays are accessed at runtime. For example, to join every other element:

```javascript
var x = [ 1, 2, 3, 4, 5, 6 ];
var sep = [ ',', '-' ];

var str = gjoinBetween( 3, '', '', x, 2, sep, 1 );
// returns '1,3-5'
```

Note that indexing is relative to the first index. To introduce an offset, use [`typed array`][mdn-typed-array] views.

```javascript
var Float64Array = require( '@stdlib/array/float64' );

// Initial array:
var x0 = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );

// Create an offset view:
var x1 = new Float64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element

// Join elements:
var sep = [ ' | ', ' | ' ];
var str = gjoinBetween( 3, '[', ']', x1, 2, sep, 1 );
// returns '[2 | 4 | 6]'
```

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#### gjoinBetween.ndarray( N, prefix, suffix, x, strideX, offsetX, separators, strideS, offsetS )

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Returns a string by joining strided array elements using a specified separator for each pair of consecutive elements and alternative indexing semantics.

```javascript
var x = [ 1, 2, 3, 4 ];
var sep = [ ' + ', ' - ', ' != ' ];

var str = gjoinBetween.ndarray( x.length, 'op: ', '', x, 1, 0, sep, 1, 0 );
// returns 'op: 1 + 2 - 3 != 4'
```

The function has the following additional parameters:

-   **offsetX**: starting index for `x`.
-   **offsetS**: starting index for `separators`.

While [`typed array`][mdn-typed-array] views mandate a view offset based on the underlying buffer, the offset parameters support indexing semantics based on starting indices. For example, to access only the last three elements of the input strided array:

```javascript
var x = [ 1, 2, 3, 4, 5, 6 ];
var sep = [ ' | ', ' | ' ];

var str = gjoinBetween.ndarray( 3, '[ ', ' ]', x, 1, x.length-3, sep, 1, 0 );
// returns '[ 4 | 5 | 6 ]'
```

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## Notes

-   If `N <= 0`, both functions return the prefix and suffix joined together.
-   The `separators` array is assumed to have at least `N-1` indexed elements (i.e., equal to the number of "gaps" between consecutive elements).
-   If an array element is either `null` or `undefined`, both functions serialize the element as an empty string.
-   Both functions support array-like objects having getter and setter accessors for array element access (e.g., [`@stdlib/array/base/accessor`][@stdlib/array/base/accessor]).

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## Examples

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

```javascript
var discreteUniform = require( '@stdlib/random/array/discrete-uniform' );
var filled = require( '@stdlib/array/base/filled' );
var gjoinBetween = require( '@stdlib/blas/ext/base/gjoin-between' );

var x = discreteUniform( 10, -100, 100, {
    'dtype': 'generic'
});
console.log( x );

var sep = filled( ' | ', x.length - 1 );
var out = gjoinBetween( x.length, '[ ', ' ]', x, 1, sep, 1 );
console.log( out );
```

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[mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray

[@stdlib/array/base/accessor]: https://www.npmjs.com/package/@stdlib/array-base-accessor

</section>

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