time-to-botec/js/node_modules/@stdlib/array/to-sparse-iterator-right/README.md

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# sparsearray2iteratorRight
> Create an iterator from a sparse array-like object, iterating from right to left.
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</section>
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<section class="usage">
## Usage
```javascript
var sparsearray2iteratorRight = require( '@stdlib/array/to-sparse-iterator-right' );
```
#### sparsearray2iteratorRight( src\[, mapFcn\[, thisArg]] )
Returns an iterator which iterates from right to left over each element in a sparse array-like `object`.
<!-- eslint-disable no-sparse-arrays -->
```javascript
var it = sparsearray2iteratorRight( [ 1, , , 4 ] );
// returns <Object>
var v = it.next().value;
// returns 4
v = it.next().value;
// returns 1
var bool = it.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.
<!-- eslint-disable no-sparse-arrays -->
```javascript
function fcn( v ) {
return v * 10.0;
}
var it = sparsearray2iteratorRight( [ 1, 2, , 4 ], fcn );
// returns <Object>
var v = it.next().value;
// returns 40.0
v = it.next().value;
// returns 20.0
// ...
```
The invoked function is provided three arguments:
- `value`: iterated value
- `index`: iterated value index
- `src`: source array-like object
<!-- eslint-disable no-sparse-arrays -->
```javascript
function fcn( v, i ) {
return v * (i+1);
}
var it = sparsearray2iteratorRight( [ 1, 2, , 4 ], fcn );
// returns <Object>
var v = it.next().value;
// returns 16
v = it.next().value;
// returns 4
v = it.next().value;
// returns 1
```
To set the callback function execution context, provide a `thisArg`.
<!-- eslint-disable no-sparse-arrays -->
```javascript
function fcn( v ) {
this.count += 1;
return v * 10.0;
}
var ctx = {
'count': 0
};
var it = sparsearray2iteratorRight( [ 1, 2, , 4 ], fcn, ctx );
// returns <Object>
var v = it.next().value;
// returns 40.0
v = it.next().value;
// returns 20.0
var count = ctx.count;
// returns 2
```
</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
- If an environment supports `Symbol.iterator`, the returned iterator is iterable.
- If provided a generic `array`, the returned iterator **ignores** holes (i.e., `undefined` values). To iterate over all generic `array` elements, use [`@stdlib/array/to-iterator-right`][@stdlib/array/to-iterator-right].
- A returned iterator does **not** copy a provided array-like `object`. To ensure iterable reproducibility, copy a provided array-like `object` **before** creating an iterator. Otherwise, any changes to the contents of an array-like `object` will be reflected in the returned iterator.
- In environments supporting `Symbol.iterator`, the function **explicitly** does **not** invoke an array's `@@iterator` method, regardless of whether this method is defined. To convert an array to an implementation defined iterator, invoke this method directly.
</section>
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## Examples
<!-- eslint no-undef: "error" -->
```javascript
var Float64Array = require( '@stdlib/array/float64' );
var inmap = require( '@stdlib/utils/inmap' );
var randu = require( '@stdlib/random/base/randu' );
var sparsearray2iteratorRight = require( '@stdlib/array/to-sparse-iterator-right' );
function scale( v, i ) {
return v * (i+1);
}
// Create an array partially filled with random numbers:
var arr = new Array( 100 );
var i;
for ( i = 0; i < arr.length; i += 2 ) {
arr[ i ] = randu();
}
// Create an iterator from the array which scales iterated values:
var it = sparsearray2iteratorRight( arr, scale );
// 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>
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[@stdlib/array/to-iterator-right]: https://www.npmjs.com/package/@stdlib/array/tree/main/to-iterator-right
</section>
<!-- /.links -->