Create an iterator from a sparse array-like object, iterating from right to left.
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> Create an iterator from a sparse array-like object, iterating from right to left.
``bash`
npm install @stdlib/array-to-sparse-iterator-right
`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.
`javascript
var it = sparsearray2iteratorRight( [ 1, , , 4 ] );
// returns
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.
`javascript
function fcn( v ) {
return v * 10.0;
}
var it = sparsearray2iteratorRight( [ 1, 2, , 4 ], fcn );
// returns
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.
`javascript
function fcn( v, i ) {
return v * (i+1);
}
var it = sparsearray2iteratorRight( [ 1, 2, , 4 ], fcn );
// returns
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.
`javascript
function fcn( v ) {
this.count += 1;
return v * 10.0;
}
var ctx = {
'count': 0
};
var it = sparsearray2iteratorRight( [ 1, 2, , 4 ], fcn, ctx );
// returns
var v = it.next().value;
// returns 40.0
v = it.next().value;
// returns 20.0
var count = ctx.count;
// returns 2
`
- If an environment supports Symbol.iterator, the returned iterator is iterable.array
- If provided a generic , 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].object
- A returned iterator does not copy a provided array-like . 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.Symbol.iterator
- In environments supporting , 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.@stdlib/array-complex64
- The returned iterator supports array-like objects having getter and setter accessors for array element access (e.g., [][@stdlib/array/complex64]).
`javascript
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 );
}
`
*
- [@stdlib/array-from-iterator][@stdlib/array/from-iterator]: create (or fill) an array from an iterator.
- [@stdlib/array-to-iterator-right][@stdlib/array/to-iterator-right]: create an iterator from an array-like object, iterating from right to left.
- [@stdlib/array-to-sparse-iterator][@stdlib/array/to-sparse-iterator]: create an iterator from a sparse array-like object.
*
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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].
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