@stdlib/iter-filter-map
v0.2.2
Published
Create an iterator which both filters and maps the values of another iterator.
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iterFilterMap
Create an iterator which both filters and maps the values of another iterator.
Installation
npm install @stdlib/iter-filter-map
Usage
var iterFilterMap = require( '@stdlib/iter-filter-map' );
iterFilterMap( iterator, fcn[, thisArg] )
Returns an iterator which both filters and maps the values of another iterator
according to a callback function.
var array2iterator = require( '@stdlib/array-to-iterator' );
function fcn( v ) {
if ( v > 2 ) {
return v * 10;
}
}
var it = iterFilterMap( array2iterator( [ 1, 3, 2, 4 ] ), fcn );
// returns <Object>
var v = it.next().value;
// returns 30
v = it.next().value;
// returns 40
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 adone
property having aboolean
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.
The callback function is provided two arguments:
value
: iterated valueindex
: iteration index (zero-based)
var array2iterator = require( '@stdlib/array-to-iterator' );
function fcn( v, i ) {
if ( i >= 2 ) {
return v * 10;
}
}
var it = iterFilterMap( array2iterator( [ 3, 4, 1, 2 ] ), fcn );
// returns <Object>
var v = it.next().value;
// returns 10
v = it.next().value;
// returns 20
var bool = it.next().done;
// returns true
To set the callback function execution context, provide a thisArg
.
var array2iterator = require( '@stdlib/array-to-iterator' );
function fcn( v ) {
this.count += 1;
if ( v > 0 ) {
return v * 10;
}
}
var ctx = {
'count': 0
};
var it = iterFilterMap( array2iterator( [ 1, 2, 3, 4 ] ), fcn, ctx );
// returns <Object>
var v = it.next().value;
// returns 10
v = it.next().value;
// returns 20
v = it.next().value;
// returns 30
var count = ctx.count;
// returns 3
Notes
- If the callback function returns
undefined
, the returned iterator invokes the callback for the next value of the providediterator
. If the callback function returns a value other thanundefined
, the returned iterator returns the callback's return value. - If an environment supports
Symbol.iterator
and a provided iterator is iterable, the returned iterator is iterable.
Examples
var randu = require( '@stdlib/random-iter-randu' );
var iterFilterMap = require( '@stdlib/iter-filter-map' );
function fcn( v ) {
if ( v > 0.5 ) {
return v * 10.0;
}
}
// Create a seeded iterator for generating pseudorandom numbers:
var rand = randu({
'seed': 1234,
'iter': 20
});
// Create an iterator which both filters and maps the generated numbers:
var it = iterFilterMap( rand, fcn );
// Perform manual iteration...
var r;
while ( true ) {
r = it.next();
if ( r.done ) {
break;
}
console.log( r.value );
}
See Also
@stdlib/iter-filter
: create an iterator which filters the values of another iterator according to a predicate function.@stdlib/iter-map
: create an iterator which invokes a function for each iterated value.
Notice
This package is part of stdlib, a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.
For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.
Community
License
See LICENSE.
Copyright
Copyright © 2016-2024. The Stdlib Authors.