iterFilterMap

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 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.

The callback function is provided two arguments:

• value: iterated value.
• index: 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